Update GitHub issue templates

.github/ISSUE_TEMPLATE/feature.md

@@ -0,0 +1,23 @@
+---
+name: Feature
+about: If you want to propose a new feature or enhancement
+labels: kind/feature
+---
+
+<!--
+
+Feel free to ask questions in #prometheus-operator on Kubernetes Slack!
+
+-->
+
+**What is missing?**
+
+**Why do we need it?**
+
+**Environment**
+
+* kube-prometheus version:
+
+    `Insert Git SHA here`
+
+**Anything else we need to know?**: