Improve our community standards (#218)

* Add a bug report template

* Add a feature request template

* Add a pull request template

* Add a security policy

* Lint newer files

.github/ISSUE_TEMPLATE/bug_report.md

@@ -0,0 +1,35 @@
+---
+name: Bug report
+about: Report a bug to improve this project
+title: ''
+labels: 'bug'
+assignees: ''
+
+---
+
+#### The bug
+
+A clear and concise description of what the bug is.
+
+#### Software versions
+
+A list of software versions where the bug is apparent, as detailed as possible:
+
+* `setup-beam`: ...
+* other (where applicable): ...
+
+#### How to replicate
+
+An ordered list of steps to replicate the bug:
+
+1. run `...`
+2. search for `...` in the error output
+3. look at file `...`
+
+#### Expected behaviour
+
+What's expected to happen when you follow the steps listed above.
+
+#### Additional context
+
+Any other context about the bug.

.github/ISSUE_TEMPLATE/feature_request.md

@@ -0,0 +1,26 @@
+---
+name: Feature request
+about: Request a feature for this project
+title: ''
+labels: 'feature'
+assignees: ''
+
+---
+
+#### Is your feature request related to a problem?
+
+A clear and concise description of what the problem is, e.g. "I'm always frustrated
+when ..."
+
+#### Describe the feature you'd like
+
+A clear and concise description of what you want to happen after the new feature
+is implemented.
+
+#### Describe alternatives you've considered
+
+A clear and concise description of any alternative solutions or features you've considered.
+
+#### Additional context
+
+Any other context about the feature request.