instrument gh action for memory usage

Author: parmentelat

.github/workflows/myst-to-pages.yml

@@ -51,7 +51,9 @@ jobs:
       - name: Build HTML Assets
         run: |
           export PYTHONPATH=$(pwd)/modules
+          free -h
           myst build --execute --html --execute-parallel 1
+          free -h
       - name: Setup Pages
         uses: actions/configure-pages@v3
       - name: Upload artifact