Add Gitleaks secret scanning workflow (#12)

Author: sklarsa

.github/workflows/gitleaks.yml

@@ -0,0 +1,19 @@
+name: Gitleaks
+
+on:
+  pull_request:
+  push:
+    branches:
+      - master
+
+jobs:
+  gitleaks:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          fetch-depth: 0
+      - uses: gitleaks/gitleaks-action@v2
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+          GITLEAKS_LICENSE: ${{ secrets.GITLEAKS_LICENSE }}