Feature request: colormap with background

Code Sample

import folium
import pandas as pd
import folium.plugins

import branca
import branca.colormap as cm

data = [
    [33.823400, -118.12194, 99.23],
    [33.823500, -118.12294, 95.23],
    [33.823600, -118.12394, 91.23],
    [33.823700, -118.12494, 90.00]
]

df = pd.DataFrame(data, columns=['latitude','longitude','data'])

x_start = (df['latitude'].max() + df['latitude'].min()) / 2
y_start = (df['longitude'].max() + df['longitude'].min()) / 2
start_coord = (x_start, y_start)


colormap = cm.LinearColormap(colors=['red','lightblue'],
                             index=[df['data'].min(),df['data'].max()],
                             vmin=df['data'].min(),vmax=df['data'].max())

colormap.caption = 'Data [units]'

map = folium.Map(location=start_coord, zoom_start=12)


lat = list(df.latitude)
lon = list(df.longitude)
dat = list(df.data)


for loc, p in zip(zip(lat, lon), dat):
    folium.Circle(
        location=loc,
        radius=10,
        fill=True,
        color=colormap(p),
        fill_opacity=0.7
    ).add_to(map)

map.add_child(colormap)
map.save('index.html')

Problem description

Code above creates colored points, and displays a colormap to show what data value each color corresponds to. This is great but it would be even better if a background colour could be selected. This slightly hacky work-around does exactly what I want:
https://stackoverflow.com/a/50427006/4988601

I'd be happy to try and plumb this into folium itself if a few people show some interest in this feature (I'm fairly new to folium so any pointers on what methods/classes I'd need to poke around in would be appreciated).

Expected Output

Colormap with an optional background color rectangle to help it stand out.

Output of folium.__version__

0.10.0

Commencez par inspecter les classes de branca.colormap et le HTML de colormap généré utilisé par l’exemple. Suivez la manière dont la colormap est rendue et déterminez où un rectangle d’arrière-plan facultatif peut être représenté ; le travail est terminé lorsque l’exemple existant prend en charge la sélection d’une couleur d’arrière-plan sans modifier le mappage des couleurs.