Add Emscripten/WASM CI build job

This is in preparation to integrate web support into our regular releases
starting with version 1.1.0.

Author: Ronsor

.github/workflows/ci.yml

@@ -108,6 +108,38 @@ jobs:
           name: ${{ matrix.target }}
           path: dist/sdk/
 
+  wasm:
+    runs-on: ubuntu-latest
+    needs: build-and-test
+    steps:
+      - uses: actions/checkout@v4
+
+      # Pinned to the emsdk version raylib 6.0's own web build used, so the
+      # archived libraylib.web.a stays ABI-compatible with this emcc.
+      - uses: emscripten-core/setup-emsdk@v15
+        with:
+          version: 5.0.3
+
+      - name: Fetch raylib v6.0 (webassembly)
+        run: |
+          mkdir -p build/raylib
+          curl -sL https://github.com/raysan5/raylib/releases/download/6.0/raylib-6.0_webassembly.zip \
+            -o build/raylib/raylib-6.0_webassembly.zip
+          ( cd build/raylib && unzip -q raylib-6.0_webassembly.zip )
+          echo "RAYLIB_WEB_DIR=$PWD/build/raylib/raylib-6.0_webassembly/include" >> "$GITHUB_ENV"
+          echo "RAYLIB_WEB_LIB=$PWD/build/raylib/raylib-6.0_webassembly/lib/libraylib.web.a" >> "$GITHUB_ENV"
+
+      - name: Build web viewer (Emscripten)
+        run: make viewer-web
+
+      - name: Upload artifacts
+        uses: actions/upload-artifact@v4
+        with:
+          name: wasm
+          path: |
+            dist/Live2DCubismCore*.js
+            dist/viewer.*
+
   release:
     if: startsWith(github.ref, 'refs/tags/v')
     runs-on: ubuntu-latest
@@ -189,4 +221,4 @@ jobs:
           files: |
             dist/PurismCore-*.zip
             dist/PurismCoreBundle-*.h
-          generate_release_notes: true
+          generate_release_notes: true