fix: remove empty line, add yaml document start line

Author: natoscott

.github/workflows/commitlint.yml

@@ -1,3 +1,4 @@
+---
 name: Commitlint
 on:  # yamllint disable-line rule:truthy
   pull_request:
@@ -28,4 +29,3 @@ jobs:
         run: >-
           echo '${{ github.event.pull_request.title }}' |
           npx commitlint --verbose
-