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

首先运行 issue 中的 Flask 复现，并在 Firefox 或 Chromium 中检查生成的 HTML 以及已加载的 Font Awesome Web 字体。跟踪 folium.Icon 如何处理 fa 前缀，并比较 solid 图标 heart 与 brand 图标 bluetooth。当两个标记都能正确渲染，并且回归检查覆盖 brand 图标时，即表示完成。