Improve on "Add Windows to the mix" (#52)

* Support more OTP+Windows versions (try to bridge the gap with gleam-lang/setup-erlang that seems to support pre-21 versions)
* Merge ci.yml and test.yml
* Add Elixir to the Windows mix
* Hopefully improve error/warning messages
* Adapt the doc.s to the current reality
* Add option version-type (loose by default, for compatibility)

src/install-elixir.ps1

@@ -1,5 +1,19 @@
-Write-Output "Installer for Elixir for Windows not available"
+param([Parameter(Mandatory=$true)][string]$VSN)
 
 $ErrorActionPreference="Stop"
 
-Exit 1
+Set-Location $Env:RUNNER_TEMP
+
+$FILE_INPUT="${VSN}.zip"
+$FILE_OUTPUT="elixir.zip"
+$DIR_FOR_BIN=".setup-beam/elixir"
+
+$ProgressPreference="SilentlyContinue"
+Invoke-WebRequest "https://repo.hex.pm/builds/elixir/${FILE_INPUT}" -OutFile "$FILE_OUTPUT"
+$ProgressPreference="Continue"
+New-Item "$DIR_FOR_BIN" -ItemType Directory | Out-Null
+$ProgressPreference="SilentlyContinue"
+Expand-Archive -DestinationPath "${DIR_FOR_BIN}" -Path "${FILE_OUTPUT}"
+$ProgressPreference="Continue"
+Write-Output "Installed Erlang/OTP version follows"
+& "$DIR_FOR_BIN/bin/iex" "-v" | Write-Output