[Doc] Create a workflow to host docs using GitHub Pages. (#28)

* [Doc] Use sphinx to generate docs.

* [Doc] Fix a bug on tlcpack_sphinx_addon.

* [Doc] Fix linting issues.

* [Doc] Create a workflow to host docs using GitHub Pages.

* [Doc] Remove all deprecated docs.

.github/workflows/publish_docs.yml

+name: documentation
+
+on: [push, pull_request, workflow_dispatch]
+
+permissions:
+  contents: write
+
+jobs:
+  docs:
+    runs-on: ubuntu-latest
+    defaults:
+      run:
+        working-directory: ./docs
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-python@v5
+      - name: Install dependencies
+        run: |
+          pip install -r requirements.txt
+      - name: Sphinx build
+        run: |
+          make html
+      - name: Deploy to GitHub Pages
+        uses: peaceiris/actions-gh-pages@v3
+        if: ${{ github.event_name == 'push' && github.ref == 'refs/heads/main' }}
+        with:
+          publish_branch: gh-pages
+          github_token: ${{ secrets.GITHUB_TOKEN }}
+          publish_dir: docs/_build/html
+          force_orphan: true