Build always, deploy only on tags

Author: microbit-grace

.github/workflows/build-docs.yml

@@ -3,6 +3,8 @@ on:
   release:
     types: [created]
   push:
+    branches:
+      - main
     tags:
       - '**'
 jobs:
@@ -22,6 +24,7 @@ jobs:
           path: ./docs/build
 
   deploy:
+    if: ${{ startsWith(github.ref, 'refs/tags/') }}
     permissions:
       pages: write
       id-token: write