👷 Add GitHub workflow to optimize PNG files (#31)

.github/workflows/optimize.yml

@@ -0,0 +1,46 @@
+name: ⚡ Optimize PNG files
+
+on:
+  push:
+    branches:
+      - mc/*
+    paths:
+      - '**/*.png'
+
+jobs:
+  build:
+    name: ⚡ Optimize PNG files
+    runs-on: ubuntu-latest
+    steps:
+      - name: 🚚 Get latest code
+        uses: actions/checkout@v3
+
+      - name: 📦 Install oxipng
+        uses: baptiste0928/cargo-install@v1
+        with:
+          crate: oxipng
+          version: latest
+
+      - name: 🧾 Get changed PNG files
+        id: changed-files
+        uses: tj-actions/changed-files@v23.2
+        with:
+          files: '**/*.png'
+
+      - name: ⚡ Optimize PNG files
+        run: oxipng -sZ -o 3 -i 0 ${{ steps.changed-files.outputs.all_changed_files }}
+
+      - name : 🧾 Get optimized PNG files
+        id: optimized-files
+        run: echo "::set-output name=all_optimized_files::$(git status --porcelain | sed s/^...// | sed -z 's/\n/%0A/g;s/%0A$/\n/')"
+
+      - name: ⬆️ Commit and push changes
+        if: ${{ steps.optimized-files.outputs.all_optimized_files }}
+        uses: swinton/commit@v2.x
+        env:
+          GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+        with:
+          files: |
+            ${{ steps.optimized-files.outputs.all_optimized_files }}
+          commit-message: ':zap: Optimize PNG files'
+          ref: ${{ github.ref }}