Add semgrep.yml

### Add semgrep.yml

#### Description
Adds an Semgrep YAML definition file semgrep.yml. This file allows Semgrep to automatically scan PR changes for vulnerabilities.

#### References
- Official Documentation: [Semgrep Documentation](https://semgrep.dev/docs/)

#### Testing
No testing is required from you as repository owners.

Author: crew-security

.github/workflows/semgrep.yml

@@ -0,0 +1,18 @@
+name: Semgrep
+
+on:
+  pull_request_target: {}
+  push:
+    branches: ["master", "main"]
+jobs:
+  semgrep:
+    name: Scan
+    runs-on: ubuntu-latest
+    container:
+      image: returntocorp/semgrep
+    if: (github.actor != 'dependabot[bot]' && github.actor != 'snyk-bot')
+    steps:
+      - uses: actions/checkout@v3
+      - run: semgrep ci
+        env:
+          SEMGREP_APP_TOKEN: ${{ secrets.SEMGREP_APP_TOKEN }}