github: add feature request issue template

.github/ISSUE_TEMPLATE/enhancement_request.md

@@ -0,0 +1,17 @@
+---
+name: Enhancement request
+about: Request a new feature or change to an existing feature
+title: ''
+labels: 'enhancement'
+assignees: ''
+
+---
+
+**Describe the enhancement**  
+<!-- A clear and concise description of what you would like added or changed. -->
+
+**Use case**  
+<!-- Tell us how you or others will use this new feature or change to an existing feature. --> 
+
+**Additional context**
+<!-- Add any other context about the enhancement here. -->