Add Erlang 24 to README and some more info on version matching (#45)

3RD_PARTY_LICENSES

@@ -209,7 +209,7 @@ THE SOFTWARE.
 
 -----
 
-The following software may be included in this product: ansi-regex, ansi-styles, callsites, chalk, has-flag, is-fullwidth-code-point, parent-module, path-key, resolve-from, shebang-regex, string-width, strip-ansi, supports-color, type-fest. A copy of the source code may be downloaded from https://github.com/chalk/ansi-regex.git (ansi-regex), https://github.com/chalk/ansi-styles.git (ansi-styles), https://github.com/sindresorhus/callsites.git (callsites), https://github.com/chalk/chalk.git (chalk), https://github.com/sindresorhus/has-flag.git (has-flag), https://github.com/sindresorhus/is-fullwidth-code-point.git (is-fullwidth-code-point), https://github.com/sindresorhus/parent-module.git (parent-module), https://github.com/sindresorhus/path-key.git (path-key), https://github.com/sindresorhus/resolve-from.git (resolve-from), https://github.com/sindresorhus/shebang-regex.git (shebang-regex), https://github.com/sindresorhus/string-width.git (string-width), https://github.com/chalk/strip-ansi.git (strip-ansi), https://github.com/chalk/supports-color.git (supports-color), https://github.com/sindresorhus/type-fest.git (type-fest). This software contains the following license and notice below:
+The following software may be included in this product: ansi-regex, ansi-styles, callsites, chalk, has-flag, is-fullwidth-code-point, parent-module, path-key, resolve-from, shebang-regex, string-width, strip-ansi, supports-color. A copy of the source code may be downloaded from https://github.com/chalk/ansi-regex.git (ansi-regex), https://github.com/chalk/ansi-styles.git (ansi-styles), https://github.com/sindresorhus/callsites.git (callsites), https://github.com/chalk/chalk.git (chalk), https://github.com/sindresorhus/has-flag.git (has-flag), https://github.com/sindresorhus/is-fullwidth-code-point.git (is-fullwidth-code-point), https://github.com/sindresorhus/parent-module.git (parent-module), https://github.com/sindresorhus/path-key.git (path-key), https://github.com/sindresorhus/resolve-from.git (resolve-from), https://github.com/sindresorhus/shebang-regex.git (shebang-regex), https://github.com/sindresorhus/string-width.git (string-width), https://github.com/chalk/strip-ansi.git (strip-ansi), https://github.com/chalk/supports-color.git (supports-color). This software contains the following license and notice below:
 
 MIT License
 

README.md

@@ -12,18 +12,19 @@ workflow by:
 - installing Erlang/OTP
 - optionally, installing Elixir
 - optionally, installing `rebar3`
+- optionally, installing `hex`
 
 **Note** Currently, this action only supports Actions' `ubuntu-` runtimes.
 
 ## Usage
 
-See [action.yml](action.yml).
+See [action.yml](action.yml) for the action's specification.
 
-**Note** The Erlang/OTP release version specification is [relatively
+**Note**: The Erlang/OTP release version specification is [relatively
 complex](http://erlang.org/doc/system_principles/versions.html#version-scheme).
 For best results, we recommend specifying exact Erlang/OTP, Elixir versions, and
 `rebar3` versions.
-However, values like `22.x` are also accepted, and we attempt to resolve them
+However, values like `22.x`, or even `>22`, are also accepted, and we attempt to resolve them
 according to semantic versioning rules.
 
 Additionally, it is recommended that one specifies Erlang/OTP, Elixir and `rebar3` versions
@@ -41,13 +42,14 @@ and Erlang/OTP.
 
 | Ubuntu       | Erlang/OTP | Status
 |-             |-           |-
-| ubuntu-16.04 | 17 - 23    | ✅
+| ubuntu-16.04 | 17 - 24    | ✅
-| ubuntu-18.04 | 17 - 23    | ✅
+| ubuntu-18.04 | 17 - 24    | ✅
-| ubuntu-20.04 | 20 - 23    | ✅
+| ubuntu-20.04 | 20 - 24    | ✅
 
 ### Basic example (Elixir)
 
 ```yaml
+# create this in .github/workflows/ci.yml
 on: push
 
 jobs:
@@ -66,6 +68,7 @@ jobs:
 ### Basic example (`rebar3`)
 
 ```yaml
+# create this in .github/workflows/ci.yml
 on: push
 
 jobs:
@@ -83,6 +86,7 @@ jobs:
 ### Matrix example (Elixir)
 
 ```yaml
+# create this in .github/workflows/ci.yml
 on: push
 
 jobs:
@@ -106,6 +110,7 @@ jobs:
 ### Matrix example (`rebar3`)
 
 ```yaml
+# create this in .github/workflows/ci.yml
 on: push
 
 jobs:
@@ -125,66 +130,6 @@ jobs:
       - run: rebar3 ct
 ```
 
-### Phoenix example
-
-```yaml
-on: push
-
-jobs:
-  test:
-    runs-on: ubuntu-latest
-
-    services:
-      db:
-        image: postgres:11
-        ports: ['5432:5432']
-        env:
-          POSTGRES_PASSWORD: postgres
-        options: >-
-          --health-cmd pg_isready
-          --health-interval 10s
-          --health-timeout 5s
-          --health-retries 5
-
-    steps:
-      - uses: actions/checkout@v2
-      - uses: erlef/setup-beam@v1
-        with:
-          otp-version: '22.2'
-          elixir-version: '1.9.4'
-      - run: mix deps.get
-      - run: mix test
-```
-
-#### Authenticating with Postgres in Phoenix
-
-When using the Phoenix example above, the `postgres` container has some
-default authentication set up. Specifically, it expects a username of
-"postgres", and a password of "postgres". It will be available at
-`localhost:5432`.
-
-The simplest way of setting these auth values in CI is by checking for the
-`GITHUB_ACTIONS` environment variable that is set in all workflows:
-
-```elixir
-# config/test.exs
-
-use Mix.Config
-
-# Configure the database for local testing
-config :app, App.Repo,
-  database: "my_app_test",
-  hostname: "localhost",
-  pool: Ecto.Adapters.SQL.Sandbox
-
-# Configure the database for GitHub Actions
-if System.get_env("GITHUB_ACTIONS") do
-  config :app, App.Repo,
-    username: "postgres",
-    password: "postgres"
-end
-```
-
 ## Elixir Problem Matchers
 
 The Elixir Problem Matchers in this repository are adapted from [here](https://github.com/fr1zle/vscode-elixir/blob/45eddb589acd7ac98e0c7305d1c2b24668ca709a/package.json#L70-L118). See [MATCHER_NOTICE](MATCHER_NOTICE.md) for license details.