Only upload docs on release

Author: dstansby

.github/workflows/docs.yml

@@ -43,7 +43,7 @@ jobs:
     name: Upload docs to GitHub pages
     runs-on: ubuntu-latest
     needs: build-docs
-    if: github.event_name == 'push' && github.ref_name == 'main'
+    if: contains(github.ref, 'tags')
     steps:
     - uses: actions/checkout@v3
     - uses: actions/download-artifact@v3