Add feature to check whether document has a valid json/jsonl format, add tests

src/easymatcher_worker.py

@@ -25,7 +25,7 @@ class EasymatcherWorker(nlp_ws.NLPWorker):
     def is_jsonl(
             document_path: str | Path
     ) -> bool:
-        """Validates whether text file has json/jsonl structure and has "text" keyword."""
+        """Validates whether text file has json/jsonl structure."""
         try:
             with open(document_path, 'r', encoding="utf-8") as file:
                 for line in file: