Add feature request issue template

.github/ISSUE_TEMPLATE/feature-request.md

@@ -0,0 +1,24 @@
+---
+name: "\U0001F31FFeature Request"
+about: Request for a new Qlib feature
+
+---
+
+## 🌟 Feature Description
+<!-- A clear and concise description of the feature proposal -->
+
+## Motivation
+
+1. Application scenario
+2. Related works (Papers, Github repos etc.):
+3. Any other relevant and important information:
+
+<!-- Please describe why the feature is important. -->
+
+## Alternatives
+
+<!-- A short description of any alternative solutions or features you've considered. -->
+
+## Additional Notes
+
+<!-- Add any other context or screenshots about the feature request here. -->