Include oxipng in CI

.github/workflows/cd.yml

@@ -15,6 +15,7 @@ env:
   MDBOOK_TOC_VERSION: "0.13.0"
   MDBOOK_ADMONISH_VERSION: "1.10.1"
   MDBOOK_BIN: "/tmp/mdbook-bin"
+  OXIPNG_VERSION: "9.0.0"
 
 # Sets permissions of the GITHUB_TOKEN to allow deployment to GitHub Pages
 permissions:
@@ -104,4 +105,31 @@ jobs:
 #        with:
 #          author_name: 'Godot-Rust Automation'
 #          author_email: '[email protected]'
-#          message: 'Auto-apply license headers'
+#          message: 'Auto-apply license headers'
+
+
+  oxipng:
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v3
+
+    - name: "Run oxipng to reduce PNG sizes"
+      run: |
+        wget https://github.com/shssoichiro/oxipng/releases/download/v${OXIPNG_VERSION}/oxipng-${OXIPNG_VERSION}-x86_64-unknown-linux-musl.tar.gz \
+        -O /tmp/oxipng.tar.gz
+        
+        tar -xvzf /tmp/oxipng.tar.gz -C /tmp
+        mv /tmp/oxipng-${OXIPNG_VERSION}-x86_64-unknown-linux-musl/oxipng ./oxipng
+        chmod +x ./oxipng
+        
+        ./oxipng --version
+        ./oxipng --strip safe --alpha -r src
+
+    - name: "Commit changes"
+      uses: EndBug/add-and-commit@v9
+      env:
+        GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+      with:
+        author_name: 'Godot-Rust Automation'
+        author_email: '[email protected]'
+        message: 'Auto-reduce PNG sizes'