Glossary: write: avoid removing trailing / from filename

allow converting to a directory with StarDict, #694

Author: ilius

pyglossary/glossary_v2.py

@@ -953,7 +953,10 @@ def _write(
 		sort: bool = False,
 		**options: Any,
 	) -> str:
+		filenameOrig = filename
 		filename = os.path.abspath(filename)
+		if filenameOrig.endswith(os.sep):
+			filename += os.sep
 
 		if formatName not in PluginHandler.plugins:
 			raise WriteError(f"No plugin {formatName!r} was found")