SemgrepAdded semgrep CI/CD scan (#25)

As a part of improving our security posture we have decided to add
Semgrep scans to public repositories therefore this commit contains the
yaml config file for semgrep to start the scans.

Author: voidd7

.github/workflows/semgrep.yml

@@ -0,0 +1,19 @@
+name: Semgrep
+on:
+  pull_request:
+  workflow_dispatch:
+
+jobs:
+  semgrep:
+    name: Run Semgrep 
+    runs-on: ubuntu-latest
+    timeout-minutes: 30
+    container:
+      # A Docker image with Semgrep installed. Do not change this.
+      image: returntocorp/semgrep
+    if: (github.actor != 'dependabot[bot]')
+    steps:
+      - uses: actions/checkout@v4
+      - run: semgrep ci
+        env:
+          SEMGREP_APP_TOKEN: ${{ secrets.SEMGREP_APP_TOKEN_PUBLIC }}