Add a myst-build job to ci workflows.

Author: rossbar

.github/workflows/ci.yml

@@ -100,3 +100,13 @@ jobs:
 
     - name: Build static site
       run: pixi run build
+
+  myst_build:
+    name: Build and execute static site with myst
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v4
+    - name: Setup environment
+      run: pip install -r requirements.txt
+    - name: Build site with execution
+      run: myst build --execute