Font Awesome Brand Icons do not work

Describe the bug

Brand icons from font-awesome do not render correctly.

To Reproduce

from flask import Flask, render_template_string

import folium

app = Flask(__name__)


@app.route("/")
def fullscreen():
    """Simple example of a fullscreen map."""
    m = folium.Map(location=[41, -71], zoom_start=4)

    folium.Marker(location=[41, -72],
        icon=folium.Icon(prefix='fa', icon='fa-heart')).add_to(m)

    folium.Marker(location=[41, -75],
        icon=folium.Icon(prefix='fa', icon='fa-bluetooth')).add_to(m)

    return m.get_root().render()


if __name__ == "__main__":
    app.run(debug=True)

Expected behavior

All icons to render correctly

Environment (please complete the following information):

• Browser: Firefox 140.15.0esr and Chromium 152.0.7977.64
• Jupyter Notebook or html files? Flask
• Python version: sys.version_info(major=3, minor=13, micro=5, releaselevel='final', serial=0)
• folium version: 0.19.5+dfsg
• branca version: 0.8.1

Additional context

It seems that the appropriate web font is not loaded. If I go to Web Developer Tools -> Inspector -> Fonts -> All Fonts on Page only https://cdn.jsdelivr.net/npm/@fortawesome/fontawesome-free@6.2.0/webfonts/fa-solid-900.woff2 is loaded and I believe the glyph for bluetooth is in https://cdn.jsdelivr.net/npm/@fortawesome/fontawesome-free@6.2.0/webfonts/fa-brands-400.woff2 so it isn't rendered correctly.

Screenshots

folium is maintained by volunteers. Can you help making a fix for this issue? Probably not

まず、issue の Flask 再現を実行し、Firefox または Chromium で生成された HTML と読み込まれた Font Awesome の Web フォントを調べます。folium.Icon が fa プレフィックスをどのように処理するかを追跡し、solid アイコンの heart と brand アイコンの bluetooth を比較します。両方のマーカーが正しくレンダリングされ、brand アイコンを対象とするリグレッションチェックが含まれていれば完了です。