Add semgrep AST scanning

.github/workflows/semgrep.yml

@@ -0,0 +1,30 @@
+name: Semgrep
+
+on:
+  push:
+    branches:
+      - main
+  pull_request:
+
+permissions:
+  contents: read
+  actions: read
+  security-events: write
+
+jobs:
+  scan:
+    runs-on: ubuntu-latest
+    container:
+      image: semgrep/semgrep
+    if: (github.actor != 'dependabot[bot]')
+    steps:
+      - uses: actions/checkout@v4
+      - run: semgrep scan --config=auto --sarif --output=semgrep.sarif
+        env:
+          SEMGREP_RULES: auto
+      - name: Upload SARIF file
+        uses: github/codeql-action/upload-sarif@v4
+        with:
+          sarif_file: semgrep.sarif
+          category: semgrep
+        if: always()