github: include date in version for labs build

Make labs version a bit easier to identify by also including the build date.

Author: dlech

.github/workflows/test-pull-request.yml

@@ -33,7 +33,7 @@ jobs:
       run: |
         echo "REACT_APP_NAME=Pybricks Labs" >> $GITHUB_ENV
         echo "REACT_APP_SUFFIX=-labs" >> $GITHUB_ENV
-        echo "REACT_APP_VERSION=$GITHUB_SHA" >> $GITHUB_ENV
+        echo "REACT_APP_VERSION=$(date --iso)-$GITHUB_SHA" >> $GITHUB_ENV
     - run: yarn build
     - uses: actions/upload-artifact@v6
       with: