add workflow for deploying doc (#129)

.github/workflows/document.yml

+name: Deploy documentation
+on:
+  pull_request:
+    types: [closed]
+    branches:
+      - '*'
+    paths:
+      - 'docs/**'
+      - 'colossalai/**'
+
+jobs:
+  build:
+    name: Build and deploy documentation
+    runs-on: [self-hosted, gpu]
+    container:
+      image: nvcr.io/nvidia/pytorch:21.07-py3
+      options: --gpus all --rm --ipc=host -v /home/gitact/.ssh:/root/ssh
+    timeout-minutes: 1200
+    if: github.base_ref == 'main' && github.event.pull_request.base.repo.full_name == 'hpcaitech/ColossalAI' && github.event.pull_request.merged == true
+    steps:
+      - name: Setup Environment
+        run: |
+          export https_proxy=http://172.17.0.1:7890 http_proxy=http://172.17.0.1:7890 all_proxy=socks5://172.17.0.1:7890
+          cp -r /root/ssh /root/.ssh
+      - name: Install dependencies
+        run: |
+          pip config set global.index-url https://pypi.tuna.tsinghua.edu.cn/simple
+          pip install -U pip setuptools wheel --user
+          pip install pytest tensorboard deepspeed apex sphinx sphinx-rtd-theme myst-parser
+      - uses: actions/checkout@v2
+      - name: Install Colossal-AI
+        run: |
+          pip install -v --no-cache-dir --global-option="--cuda_ext" .
+      - name: Build documentation
+        run: |
+          cd docs
+          rm -rf colossalai
+          make apidoc
+          make html
+      - name: Deploy documentation
+        run: |
+          scp -r docs/.build/html server:/home/shared/web/html/colossalai-doc