migrate usage.py to dash 2.0

Author: etpinard

{{cookiecutter.project_shortname}}/usage.py

@@ -1,9 +1,7 @@
 import {{cookiecutter.project_shortname}}
-import dash
-from dash.dependencies import Input, Output
-import dash_html_components as html
+from dash import Dash, callback, html, Input, Output
 
-app = dash.Dash(__name__)
+app = Dash(__name__)
 
 app.layout = html.Div([
     {{cookiecutter.project_shortname}}.{{cookiecutter.component_name}}(
@@ -15,7 +13,7 @@
 ])
 
 
-@app.callback(Output('output', 'children'), [Input('input', 'value')])
+@callback(Output('output', 'children'), Input('input', 'value'))
 def display_output(value):
     return 'You have entered {}'.format(value)