Add back the emscripten toolchain

Author: oscarbenjamin

.github/workflows/ci-emscripten.yml

@@ -16,6 +16,7 @@ jobs:
     runs-on: ubuntu-latest
     env:
       PYTHON_VERSION: 3.13 # any 3.13.x version works
+      EMSCRIPTEN_VERSION: 4.0.9
       NODE_VERSION: 22
     steps:
       - uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd  # v6.0.2
@@ -25,6 +26,12 @@ jobs:
         with:
           python-version: ${{ env.PYTHON_VERSION }}
 
+      - name: Set up Emscripten toolchain
+        uses: mymindstorm/setup-emsdk@6ab9eb1bda2574c4ddb79809fc9247783eaf9021 # v14
+        with:
+          version: ${{ env.EMSCRIPTEN_VERSION }}
+          actions-cache-folder: emsdk-cache
+
       - name: Set up Node.js
         uses: actions/setup-node@v6
         with: