Move license header check into its own workflow

.github/workflows/pr_ci_backend.yaml

@@ -69,6 +69,3 @@ jobs:
           . .venv/bin/activate
           python ./backend/manage.py makemigrations
           python ./backend/manage.py migrate
-
-      - name: Check License Header
-        uses: apache/skywalking-eyes/header@main

.github/workflows/pr_ci_frontend.yaml

@@ -45,6 +45,3 @@ jobs:
         if: always()
         working-directory: ./frontend
         run: sudo yarn test
-
-      - name: Check License Header
-        uses: apache/skywalking-eyes/header@main

.github/workflows/pr_ci_license_header_check.yaml

@@ -0,0 +1,14 @@
+name: pr_ci_license_header_check
+on:
+  pull_request:
+    branches:
+      - main
+    types: [opened, reopened, synchronize]
+
+jobs:
+  frontend:
+    name: Run PR License Header Check
+    runs-on: ubuntu-latest
+    steps:
+      - name: Check License Header
+        uses: apache/skywalking-eyes/header@main

.licenserc.yaml

@@ -1,4 +1,4 @@
- header:
+header:
   license:
     content: "SPDX-License-Identifier: AGPL-3.0-or-later"
   paths: