PR template: Feature -> functionality change

Feature might be misinterpreted in some cases. This label should be about
functionality in backward compatible way. That means that this is either
deprecating some current one or adding new functionality.

Functionality change should cover:
- adding configuration
- deprecating functionality
- adding new functionality

This change would go automatically to feature release.

Author: 0xc0170

.github/pull_request_template.md

@@ -19,6 +19,6 @@
     [ ] Fix
     [ ] Refactor
     [ ] Target update
-    [ ] Feature
+    [ ] Functionality change
     [ ] Breaking change