[core] Add Issue and Pull Request Template

This commit adds two issue templates and a pull request template. A user
can now select between reporting a bug or requesting a new feature when
opening an issue. The pull request template provides some guidance on
naming the pull request and on the required description.

.github/ISSUE_TEMPLATE/feature_request.md

@@ -0,0 +1,31 @@
+---
+name: Feature request
+about: Suggest an idea for this project
+title: '[<SOURCE>]'
+labels: enhancement
+assignees: ''
+
+---
+
+<!--
+  Please add the source type for your bug to the title of the issue, e.g. "[rss] RSS Feed could not be parsed". When
+  your problem is not related to a source use "core", e.g. "[core] Feature xyz is not working"
+-->
+
+## Is your feature request related to a problem? Please describe
+
+A clear and concise description of what the problem is. Ex. I'm always
+frustrated when [...]
+
+## Describe the solution you'd like
+
+A clear and concise description of what you want to happen.
+
+## Describe alternatives you've considered
+
+A clear and concise description of any alternative solutions or features you've
+considered.
+
+## Additional context
+
+Add any other context or screenshots about the feature request here.