External html widget i dash

Dash is great, but I can’t figure out how to incorporate external html widgets.
Examples are https://www.buymeacoffee.com for monetizing the application, or social sharing widgets like ShareThis: Free Social Share Buttons & Plugins for Websites & Blogs, and a lot of similar widgets.

All of those deliver an html code they want me to paste between the <head> and </head> section of the website.

I can not find out how to set the head tag in Dash?

I found the solution here: https://dash.plotly.com/external-resources

paste the code between <head> and </head>

app.index_string = '''
<!DOCTYPE html>
<html>
    <head>
        <script "script here"> </script>
        {%metas%}
        <title>{%title%}</title>
        {%favicon%}
        {%css%}
    </head>
    <body>
        <div>My Custom header</div>
        {%app_entry%}
        <footer>
            {%config%}
            {%scripts%}
            {%renderer%}
        </footer>
        <div>My Custom footer</div>
    </body>
</html>
'''