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>
        <script "script here"> </script>
        <div>My Custom header</div>
        <div>My Custom footer</div>