cli/validate: fail on errors

src/cli/validate.py

@@ -3,15 +3,20 @@ from lib_marker import Point, Track
 
 
 def main() -> None:
+    result_is_ok = True
     for test_name, test_f in _tests.items():
         results = test_f()
         if len(results) > 0:
+            result_is_ok = False
             print(f"[X] {test_name}")
             for result in results:
                 print(f"  {result}")
         else:
             print(f"[✓] {test_name}")
 
+    if not result_is_ok:
+        exit(1)
+
 
 def validate_no_non_included_files() -> list:
     # TODO: Implement this function