Front matter linter

packages/df-wiki-cli/df_wiki_cli/content/main.py

 import typer
+import sys
 from typing_extensions import Annotated
 from typing import Optional, List
 from pathlib import Path
@@ -71,5 +72,7 @@ def lint(
                 console.print(
                     f"[red]{err['msg']} : {err['type']} {' -> '.join([str(l) for l in err['loc']])}"
                 )
+            # raise
+            sys.exit(1)
         else:
             console.print("[green] Everything is alright")