Update issue templates

Author: jim-parry

.github/ISSUE_TEMPLATE/feature_request.md

@@ -0,0 +1,11 @@
+---
+name: Feature request
+about: How to submit a feature request
+title: ''
+labels: ''
+assignees: ''
+
+---
+
+Please submit feature requests to our [forum](https://forum.codeigniter.com/forum-29.html).
+We use github issues to track bugs and planned work.