add indentation cd checking

.github/workflows/check_indentation.yml

@@ -0,0 +1,18 @@
+name: Check indentation
+
+on:
+  push:
+    branches: [ "main" ]
+  pull_request:
+    branches: [ "main" ]
+
+jobs:
+  build:
+
+    runs-on: ubuntu-latest
+
+    steps:
+    - uses: actions/checkout@v4
+
+    - name: Check tabs
+      run: make test_tabs