use open sans as fallback

Author: marcoow

.github/workflows/ci.yml

@@ -29,6 +29,12 @@ jobs:
           sudo cp -r core-sans-a-fonts/* /usr/local/share/fonts/
           sudo fc-cache -f -v
           fc-list | grep "Core Sans"
+      - name: Use Fallback find for fork PRs
+        if: "github.event.pull_request.head.repo.fork"
+        run: |
+          sed -i 's/CoreSansA45.ttf/OpenSans-Regular.ttf/g' book/book.toml
+          sed -i 's/CoreSansA45It.ttf/OpenSans-Italic.ttf/g' book/book.toml
+          sed -i 's/CoreSansA65It.ttf/OpenSans-BoldItalic.ttf/g' book/book.toml
       - uses: actions-rust-lang/setup-rust-toolchain@v1
       - name: Install exercise plugin
         run: cargo install --path helpers/mdbook-exercise-linker