Adding Semgrep and Codeowner file

Author: yogendrasrivastava

.github/workflows/CODEOWNER

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+# CODEOWNERS
+* @upstox-security-review

.github/workflows/semgrep.yml

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+on:
+  workflow_dispatch: {}
+  pull_request: {}
+  push:
+    branches:
+      - main
+    paths:
+      - .github/workflows/semgrep.yml
+  schedule:
+    # random HH:MM to avoid a load spike on GitHub Actions at 00:00
+    - cron: '45 13 * * *'
+
+name: Semgrep
+
+jobs:
+  semgrep:
+    name: semgrep/ci
+    runs-on: ubuntu-20.04
+    env:
+      SEMGREP_APP_TOKEN: ${{ secrets.SEMGREP_APP_TOKEN }}
+    container:
+      image: returntocorp/semgrep
+    steps:
+      - uses: actions/checkout@v3
+      - run: |
+          echo "Running semgrep"
+          semgrep ci
+
+  approve:
+    name: Approve PR if Semgrep passes
+    runs-on: ubuntu-20.04
+    needs: semgrep
+    steps:
+      - name: Setup GitHub CLI
+        uses: actions/checkout@v3
+      - name: Approve PR
+        if: success()
+        run: gh pr review --approve "${{ github.event.pull_request.html_url }}"
+        env:
+          GITHUB_TOKEN: ${{ secrets.PAT_SECURITYREVIEWUSER }}