ci: add include-markdown for mkdocs (#100)

.github/workflows/deploy_docs.yaml

@@ -24,7 +24,7 @@ jobs:
     - name: Install dependencies
       run: |
         python -m pip install --upgrade pip
-        pip install mkdocs mkdocs-material
+        pip install mkdocs mkdocs-material mkdocs-include-markdown-plugin
 
     - name: Build the documentation
       run: mkdocs build