Update .github/workflows/build_icons.yml

Co-authored-by: Clemens Bastian <8781699+amacado@users.noreply.github.com>

.github/workflows/build_icons.yml

@@ -1,5 +1,13 @@
 name: Build Icons
-on: push
+on:
+  # Trigger the workflow on push or pull request,
+  # but only for the master branch
+  push:
+    branches:
+      - master
+  pull_request:
+    branches:
+      - master
 
 jobs:
   build:
@@ -22,4 +30,4 @@ jobs:
       - name: Commit changes
         uses: stefanzweifel/git-auto-commit-action@v4
         with:
-          commit_message: Built new icons, icomoon.json and devicon.css
+          commit_message: Built new icons, icomoon.json and devicon.css