Rename config.json.example

it's really the config dedicated to bittrex,
so the name should reflect this in beeing config_bittrex.json.example

tests/test_arguments.py

@@ -172,7 +172,7 @@ def test_download_data_options() -> None:
 def test_plot_dataframe_options() -> None:
     args = [
         'plot-dataframe',
-        '-c', 'config.json.example',
+        '-c', 'config_bittrex.json.example',
         '--indicators1', 'sma10', 'sma100',
         '--indicators2', 'macd', 'fastd', 'fastk',
         '--plot-limit', '30',