Add support for tab completion (#12411)

* Add support for tab completion

* make flake8 happy

* Add documentation

lib/python/qmk/cli/kle2json.py

@@ -4,6 +4,7 @@ import json
 import os
 from pathlib import Path
 
+from argcomplete.completers import FilesCompleter
 from milc import cli
 from kle2xy import KLE2xy
 
@@ -11,7 +12,7 @@ from qmk.converter import kle2qmk
 from qmk.json_encoders import InfoJSONEncoder
 
 
-@cli.argument('filename', help='The KLE raw txt to convert')
+@cli.argument('filename', completer=FilesCompleter('.json'), help='The KLE raw txt to convert')
 @cli.argument('-f', '--force', action='store_true', help='Flag to overwrite current info.json')
 @cli.subcommand('Convert a KLE layout to a Configurator JSON', hidden=False if cli.config.user.developer else True)
 def kle2json(cli):