chore(ci): improve docs build (#113)

* chore(ci): improve docs build

* fix(ci): trying to fix cache dir

* chore(ci): split caching in two steps

.github/workflows/pages.yml

@@ -6,6 +6,8 @@ on:
   push:
     branches: ["main"]
 
+  pull_request:
+
   # Allows you to run this workflow manually from the Actions tab
   workflow_dispatch:
 
@@ -45,17 +47,31 @@ jobs:
         run: pip install manim sphinx sphinx_click furo
       - name: Install local Python package
         run: poetry install --with docs
+      - name: Restore cached media
+        id: cache-media-restore
+        uses: actions/cache/restore@v3
+        with:
+          path: media
+          key: ${{ runner.os }}-media
       - name: Build animation and convert it into HTML slides
         run: |
           poetry run manim example.py ConvertExample
           poetry run manim-slides convert ConvertExample docs/source/_static/slides.html -ccontrols=true
+      - name: Save media to cache
+        id: cache-media-save
+        uses: actions/cache/save@v3
+        with:
+          path: media
+          key: ${{ steps.cache-media-restore.outputs.cache-primary-key }}
       - name: Build docs
         run: cd docs && poetry run make html
       - name: Upload artifact
+        if: github.event_name != 'pull_request'
         uses: actions/upload-pages-artifact@v1
         with:
           # Upload docs/build/html dir
           path: 'docs/build/html/'
       - name: Deploy to GitHub Pages
         id: deployment
+        if: github.event_name != 'pull_request'
         uses: actions/deploy-pages@v1