Update feature issue template

When opening #536, I noticed the **feature** label wasn't applied automatically. Guessing it must match the exact name in the template.

Author: victorlin

.github/ISSUE_TEMPLATE/feature_request.md

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