Don't publish on the push of any tag

The tags are named vX.Y, and we'll be 0.x for a while, so limiting the
publish-crate action to run v0 tags seems good enough to avoid
accidental publishes.

Author: nickolay

.github/workflows/rust.yml

@@ -65,7 +65,7 @@ jobs:
         github-token: ${{ secrets.GITHUB_TOKEN }}
 
   publish-crate:
-    if: startsWith(github.ref, 'refs/tags/')
+    if: startsWith(github.ref, 'refs/tags/v0')
     runs-on: ubuntu-latest
     needs: [test]
     steps: