Revise GitHub templates

- Separate templates into bug report and feature request
- Add a checklist and guidance comments
- Add a PR template
- Add SUPPORT.md

.github/SUPPORT.md

@@ -0,0 +1,18 @@
+# Support Resources
+
+The issue tracker is only for bug reports/feature requests related to the project itself.
+
+Please do not use the issue tracker for questions about general program usage,
+how BitTorrent (the protocol) works in general, etc.
+
+For such questions, use one of the following community support resources:
+
+* The [discussions section][discussions-url]
+
+* The official forum [official forum][forum-url]
+
+* The [qBittorrent subreddit][subreddit-url]
+
+[discussions-url]: https://github.com/qbittorrent/qBittorrent/discussions
+[forum-url]: http://forum.qbittorrent.org/
+[subreddit-url]: https://www.reddit.com/r/qBittorrent/