fix: indentation

.github/workflows/typst.yml

@@ -1,10 +1,9 @@
 name: Build Typst document
-on:
-  push: main
-  pull_request: main
+on: [push, pull_request]
 jobs:
   typst-build:
     runs-on: ubuntu-latest
+    if: ${{ github.ref == 'refs/heads/main' }}
     steps:
       - uses: actions/checkout@v3
       - name: Build Typst