Add a template for feature request issues instructing user to not create them

Also provide direction for users who are willing to contribute code for new features themselves

.github/ISSUE_TEMPLATE/feature_request.md

@@ -0,0 +1,13 @@
+---
+name: Feature Request
+about: Request a new feature
+title: ''
+labels: feature
+assignees: ''
+---
+
+**PLEASE DO NOT OPEN FEATURE REQUEST ISSUES ON GITHUB**
+
+**Feature requests should be opened up on our dedicated [feature request hub](https://features.jellyfin.org/) so that they can be appropriately discussed and prioritized.**
+
+If you are willing to contribute to the project by adding a new feature yourself, then please ensure that you first review our [documentation on contributing code](https://jellyfin.org/docs/general/contributing/development.html). Once you have reviewed the documentation feel free to come back here and open an issue here outlining your proposed approach so that it can be documented, tracked and discussed by other team members.