Meta: update repository files

See https://github.com/whatwg/spec-factory for details.

.github/workflows/build.yml

@@ -0,0 +1,26 @@
+name: Build
+on:
+  pull_request:
+    branches:
+    - master
+  push:
+    branches:
+    - master
+jobs:
+  build:
+    name: Build
+    runs-on: ubuntu-20.04
+    steps:
+    - uses: actions/checkout@v2
+      with:
+        fetch-depth: 2
+    # Note: `python` will also be this version, which various scripts depend on.
+    - uses: actions/setup-python@v2
+      with:
+        python-version: 3.8
+    # Note: `make deploy` will do a deploy dry run on PRs.
+    - run: make deploy
+      env:
+        SERVER: ${{ secrets.MARQUEE_SERVER }}
+        SERVER_PUBLIC_KEY: ${{ secrets.MARQUEE_PUBLIC_KEY }}
+        SERVER_DEPLOY_KEY: ${{ secrets.MARQUEE_DEPLOY_KEY }}

.gitignore

@@ -1,6 +1,4 @@
 /fullscreen.spec.whatwg.org/
 /deploy.sh
-/deploy_key
-/deploy_key.pub
 /fullscreen.html
 /review.sh