CI: add a job to build docs

Would be useful for contributors or people planning to use libgir

.github/workflows/docs.yml

@@ -0,0 +1,32 @@
+name: docs
+
+on:
+  pull_request:
+  push:
+    branches:
+      - "master"
+  workflow_dispatch:
+
+jobs:
+  build-deploy:
+    runs-on: ubuntu-22.04
+    steps:
+      - uses: actions/checkout@v3
+      - uses: actions-rs/toolchain@v1
+        with:
+          profile: minimal
+          toolchain: stable
+          override: true
+      - uses: actions-rs/cargo@v1
+        with:
+          command: doc
+          args: --no-deps
+
+      - name: Deploy
+        uses: peaceiris/actions-gh-pages@v3
+        if: ${{ github.event_name == 'push' && github.ref == 'refs/heads/master' }}
+        with:
+          github_token: ${{ secrets.GITHUB_TOKEN }}
+          publish_dir: ./target/doc
+          keep_files: false
+          destination_dir: docs

README.md

@@ -5,3 +5,5 @@
 ## How to use
 
 A work in progress book to help with learning how to use `gir` along with a tutorial are available at <https://gtk-rs.org/gir/book>.
+
+If you intend to contribute to `gir` or make use of `libgir`, the docs are available at <https://gtk-rs.org/gir/docs/gir> / <https://gtk-rs.org/gir/docs/libgir>.