docs(ci): install mkdocs-material and plugins for gh-deploy

Author: Karthikprasadm

.github/workflows/docs.yml

@@ -23,7 +23,7 @@ jobs:
       - name: Install mkdocs
         run: |
           python -m pip install --upgrade pip
-          python -m pip install mkdocs
+          python -m pip install mkdocs mkdocs-material mkdocs-minify-plugin mkdocs-git-revision-date-localized-plugin
 
       - name: Build and deploy
         working-directory: sup-lang