Update issue templates

Added feature request template.

.github/ISSUE_TEMPLATE/bug_report.md

@@ -2,10 +2,8 @@
 name: Bug report
 about: Create a report to help us improve
 title: "[BUG] (Insert short description)"
+labels: ''
 assignees: ''
-labels: 
-
-- bug
 
 ---
 

.github/ISSUE_TEMPLATE/feature_request.md

@@ -0,0 +1,17 @@
+---
+name: Feature request
+about: Suggest an idea for this project
+title: "[FEATURE REQUEST] (Insert a short description)"
+labels: enhancement
+assignees: ''
+
+---
+
+## Is your feature request related to a problem? Please describe.
+A clear and concise description of what the problem is. Ex. I'm always frustrated when [...] or it would be great if Pistache could do [...].
+
+## Describe the solution you'd like
+A clear and concise description of what you want to happen.
+
+## Additional Context
+Add any other context or screenshots about the feature request here.