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

src/easymatcher_worker.py

@@ -20,9 +20,12 @@ class EasymatcherWorker(nlp_ws.NLPWorker):
     It relies on the use of an easymatcher tool which can be found he under -
     https://gitlab.clarin-pl.eu/knowledge-extraction/tools/easymatcher
     """
+
     @staticmethod
-    def is_jsonl(document_path: str | Path) -> bool:
-        """Validates whether text file has json/jsonl structure and has "text" keyword"""
+    def is_jsonl(
+            document_path: str | Path
+    ) -> bool:
+        """Validates whether text file has json/jsonl structure and has "text" keyword."""
         try:
             with open(document_path, 'r', encoding="utf-8") as file:
                 for line in file: