Add Siftleft scan

It seems [to cover](https://slscan.io/en/latest/#supported-languages-frameworks) PHP including license check in addition to dependency scanning.

.github/workflows/shiftleft-analysis.yml

@@ -0,0 +1,35 @@
+# This workflow integrates Scan with GitHub's code scanning feature
+# Scan is a free open-source security tool for modern DevOps teams from ShiftLeft
+# Visit https://slscan.io/en/latest/integrations/code-scan for help
+name: SL Scan
+
+on:
+  push:
+    branches: [ master ]
+  pull_request:
+    # The branches below must be a subset of the branches above
+    branches: [ master ]
+  schedule:
+    - cron: '16 22 * * 4'
+
+jobs:
+  Scan-Build:
+    # Scan runs on ubuntu, mac and windows
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v2
+    # potentially add composer install steo here
+    - name: Perform Scan
+      uses: ShiftLeftSecurity/scan-action@master
+      env:
+        WORKSPACE: ""
+        GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+        SCAN_AUTO_BUILD: true
+      with:
+        output: reports
+        # Scan auto-detects the languages.
+
+    - name: Upload report
+      uses: github/codeql-action/upload-sarif@v1
+      with:
+        sarif_file: reports