ci: add CodeQL workflow so it runs on fork PRs

The default setup CodeQL doesn't trigger on PRs from forks, which
blocks merging when CodeQL is a required status check.

Author: benben

.github/workflows/codeql.yml

@@ -0,0 +1,28 @@
+name: "CodeQL"
+
+on:
+  push:
+    branches:
+      - main
+  pull_request:
+    branches:
+      - main
+
+permissions:
+  contents: read
+  security-events: write
+
+jobs:
+  analyze:
+    name: Analyze
+    runs-on: ubuntu-24.04-arm
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-go@v5
+        with:
+          go-version-file: go.mod
+      - uses: github/codeql-action/init@v3
+        with:
+          languages: go
+      - uses: github/codeql-action/autobuild@v3
+      - uses: github/codeql-action/analyze@v3