Add GITHUB_TOKEN to MkDocs deployment workflow for explicit authentication

Author: yibeichan

.github/workflows/deploy_mkdocs.yml

@@ -26,3 +26,5 @@ jobs:
       - name: Deploy docs
         run: |
           mkdocs gh-deploy --force --clean
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}