Cleanups + prefer .yaml (#3069)

Co-authored-by: Robert Kaussow <xoxys@rknet.org>

.pre-commit-config.yaml

@@ -35,6 +35,14 @@ repos:
     hooks:
       - id: yamllint
         args: [--strict, -c=.yamllint.yaml]
+  - repo: local
+    hooks:
+      - id: yaml-file-extension
+        name: Check if YAML files has *.yaml extension.
+        entry: YAML filenames must have .yaml extension.
+        language: fail
+        files: .yml$
+        exclude: '^.gitpod.yml$'
 
 ci:
   autofix_commit_msg: |