[workflow] added doc build test

.github/workflows/check_doc_on_pr.yml

@@ -21,3 +21,48 @@ jobs:
           python-version: '3.8.14'
 
       - run: python .github/workflows/scripts/check_doc_i18n.py -d docs/source
+
+  check-doc-build:
+    name: Test if the docs can be built
+    if: |
+        github.event.pull_request.draft == false &&
+        github.base_ref == 'main' &&
+        github.event.pull_request.base.repo.full_name == 'hpcaitech/ColossalAI'
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+        with:
+          path: './ColossalAI'
+          fetch-depth: 0
+
+      - uses: actions/checkout@v2
+        with:
+          path: './ColossalAI-Documentation'
+          repository: 'hpcaitech/ColossalAI-Documentation'
+
+      - uses: actions/setup-python@v2
+        with:
+          python-version: '3.8.14'
+
+      - run: |
+          ls -la
+          ls -la ..
+
+      # we use the versions in the main branch as the guide for versions to display
+      # checkout will give your merged branch
+      # therefore, we need to make the merged branch as the main branch
+      - name: Make the merged branch main
+        run: |
+          cd ColossalAI
+          curBranch=$(git rev-parse --abbrev-ref HEAD)
+          git checkout main
+          git merge $curBranch             # fast-forward master up to the merge
+
+      - name: Build docs
+        run: |
+          cache_dir=ColossalAI-Documentation/doc-build/.cache
+          mkdir $cache_dir
+          mv ColossalAI $cache_dir
+          cd ColossalAI-Documentation
+          pip install -v ./doc-build
+          bash ./scripts/build.sh