Fix file permissions before deployment to GitHub Pages

See actions/deploy-pages#188 (comment)
for more details.

This will avoid timeouts like this:

    Getting Pages deployment status...
    Current status: deployment_perms_error
    Getting Pages deployment status...
    Current status: deployment_perms_error
    Error: Timeout reached, aborting!
    Error: Timeout reached, aborting!

.github/workflows/pages.yml

@@ -42,6 +42,14 @@ jobs:
       - name: Stage WASM
         run: mv web/dist dist/app
 
+      - name: Fix file permissions
+        shell: sh
+        run: |
+          chmod -c -R +rX dist |
+          while read line; do
+            echo "::warning title=Invalid file permissions automatically fixed::$line"
+          done
+
       - name: Setup Pages
         uses: actions/configure-pages@v2
       - name: Upload artifact