Only run publish workflow on main monaco-editor repo

Signed-off-by: Matthew Peveler <matt@popsql.com>

.github/workflows/publish.yml

@@ -12,6 +12,7 @@ on:
         default: 'true'
 jobs:
   publish:
+    if: github.repository == "microsoft/monaco-editor"
     name: Publish to npm
     runs-on: ubuntu-latest
     steps: