Define CI build workflow

.github/workflows/ci-build.yml

@@ -0,0 +1,21 @@
+name: CI build
+
+on:
+  push:
+    branches: [ "master" ]
+  pull_request:
+    branches: [ "master" ]
+
+jobs:
+  build:
+
+    runs-on: ubuntu-latest
+
+    steps:
+    - uses: actions/checkout@v4
+    - name: Setup Emscripten toolchain
+      uses: mymindstorm/setup-emsdk@v14
+      with:
+        version: 3.1.71
+    - name: build
+      run: ./build.sh