chore(docs): use RTD (#365)

* chore(docs): use RTD

* chore(ci): remove pages deployment

.github/workflows/pages.yml

@@ -1,97 +0,0 @@
-# Simple workflow for deploying static content to GitHub Pages
-name: Deploy static content to Pages
-
-on:
-  # Runs on pushes targeting the default branch
-  push:
-    branches: [main]
-
-  pull_request:
-
-  # Allows you to run this workflow manually from the Actions tab
-  workflow_dispatch:
-
-# Sets permissions of the GITHUB_TOKEN to allow deployment to GitHub Pages
-permissions:
-  contents: read
-  pages: write
-  id-token: write
-
-# Allow one concurrent deployment
-concurrency:
-  group: pages
-  cancel-in-progress: true
-
-jobs:
-  # Single deploy job since we're just deploying
-  deploy:
-    permissions: write-all
-    environment:
-      name: github-pages
-      url: ${{ steps.deployment.outputs.page_url }}
-    runs-on: ubuntu-latest
-    steps:
-    - name: Checkout
-      uses: actions/checkout@v4
-
-    - name: Install PDM
-      uses: pdm-project/setup-pdm@v4
-      with:
-        python-version: '3.10'
-        cache: true
-
-    - name: Setup Pages
-      uses: actions/configure-pages@v4
-
-    - name: Install Linux Dependencies
-      run: |
-        sudo apt-get update
-        sudo apt-get install libcairo2-dev libpango1.0-dev ffmpeg freeglut3-dev
-
-    - name: Setup Pandoc
-      uses: nikeee/setup-pandoc@v1
-
-    - name: Install local Python package
-      run: pdm sync -Gdocs -Ggithub-action
-
-    - name: Install IPython kernel
-      run: pdm run ipython kernel install --name "manim-slides" --user
-
-    - name: Restore cached media
-      id: cache-media-restore
-      uses: actions/cache/restore@v4
-      with:
-        path: docs/media
-        key: ${{ runner.os }}-docs-media
-
-    - name: Clear cache
-      run: |
-        gh extension install actions/gh-actions-cache
-        gh actions-cache delete ${{ steps.cache-media-restore.outputs.cache-primary-key }} --confirm || true
-      env:
-        GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
-
-    - name: Save media to cache
-      id: cache-media-save
-      uses: actions/cache/save@v4
-      with:
-        path: docs/media
-        key: ${{ steps.cache-media-restore.outputs.cache-primary-key }}
-
-    - name: Build docs
-      run: cd docs && pdm run make html
-
-    - name: Upload artifact
-      if: github.event_name != 'pull_request'
-      uses: actions/upload-pages-artifact@v3
-      with:
-        # Upload docs/build/html dir
-        path: docs/build/html/
-
-    - name: Show docs/build/html/_static/ dir content (video only)
-      run: tree -L 3 docs/build/html/_static/ -P '*.mp4'
-
-    - name: Deploy to GitHub Pages
-      id: deployment
-      if: github.event_name != 'pull_request'
-      uses: actions/deploy-pages@v4