github: build HTML on Actions

Author: yosida95

.github/workflows/build.yaml

@@ -0,0 +1,18 @@
+---
+name: build
+on:
+  pull_request:
+    branches: [master]
+permissions:
+  contents: read
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v6
+      - uses: actions/setup-python@v5
+        with:
+          python-version: '3.10'
+          cache: 'pip'
+      - run: pip install -r requirements.txt
+      - run: make html