add labels to issue templates (#2660)

- added "bug" to bug template
- added "enhancement" to feature request template

.github/ISSUE_TEMPLATE/bug_report.md

@@ -2,7 +2,7 @@
 name: Bug report
 about: Create a report to help us improve
 title: ''
-labels: ''
+labels: 'bug'
 assignees: ''
 ---
 

.github/ISSUE_TEMPLATE/feature_request.md

@@ -2,7 +2,7 @@
 name: Feature request
 about: Suggest an idea for this project
 title: ''
-labels: ''
+labels: 'enhancement'
 assignees: ''
 
 ---