Add SonarQube scan workflow

.forgejo/workflows/sonarqube-scan.yml

@@ -0,0 +1,21 @@
+name: SonarQube Scan
+on: [push]
+jobs:
+  sonarqube:
+    runs-on: docker
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          fetch-depth: 0
+      - name: Set project key
+        id: vars
+        run: echo "key=$(echo '${{ github.repository }}' | tr '/' '_')" >> "$GITHUB_OUTPUT"
+      - uses: sonarsource/sonarqube-scan-action@v5
+        env:
+          SONAR_TOKEN: ${{ secrets.SONAR_TOKEN }}
+          SONAR_HOST_URL: ${{ secrets.SONAR_HOST_URL }}
+        with:
+          args: >
+            -Dsonar.projectKey=${{ steps.vars.outputs.key }}
+            -Dsonar.projectName=${{ github.repository }}
+            -Dsonar.sources=.