Make FileInput Button adhere to the design

[hoxbro]

import panel as pn

pn.extension(design="bootstrap")

file_input_stylesheet = """
input[type="file"].bk-input {
  padding-left: 10px;
}
input[type="file"]::file-selector-button {
  background: var(--surface-color);
  color: var(--surface-text-color);
}
"""

pn.widgets.FileInput().servable()
pn.widgets.Button(name="Button").servable()
pn.widgets.FileInput(stylesheets=[file_input_stylesheet]).servable()