feat: 🎸 add semgrep.yml

.github/workflows/semgrep.yml

@@ -0,0 +1,18 @@
+name: Semgrep
+
+on: pull_request
+
+jobs:
+  semgrep:
+    name: Scan
+    runs-on: ubuntu-latest
+    if: (github.actor != 'dependabot[bot]')
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v2
+
+      - uses: returntocorp/semgrep-action@v1
+        with:
+          config: >-
+            p/security-audit
+            p/secrets