convert tags to lower case to avoid import issues

See laurent22/joplin#11179

src/importer.py

@@ -222,7 +222,10 @@ def write_note(self, note: imf.Note):
                 # Arbitrary metadata will be ignored.
                 metadata = {}
                 if note.tags:
-                    metadata["tags"] = [tag.title for tag in note.tags]
+                    # Convert the tags to lower case before the import to avoid issues
+                    # with special first characters.
+                    # See: https://github.com/laurent22/joplin/issues/11179
+                    metadata["tags"] = [tag.title.lower() for tag in note.tags]
                 supported_keys = [
                     "title",
                     "created",