chore: Add Semgrep static analysis scans (#96)

Author: mpast

.github/workflows/semgrep.yml

@@ -0,0 +1,16 @@
+name: Semgrep
+on:
+  pull_request: {}
+  push:
+    branches:
+      - main
+jobs:
+  semgrep:
+    name: Scan
+    runs-on: ubuntu-latest
+    if: (github.actor != 'dependabot[bot]')
+    steps:
+      - uses: actions/checkout@v2
+      - uses: returntocorp/semgrep-action@v1
+        with:
+          publishToken: ${{ secrets.SEMGREP_APP_TOKEN }}