Those are just images generated by a website like shields.io (but other websites offer similar services)
For example these badges (From Typewriter extension):
Are achieved with this Markdown code:
[](https://github.com/clarkwinkelmann/flarum-ext-typewriter/blob/master/LICENSE.md) [](https://packagist.org/packages/clarkwinkelmann/flarum-ext-typewriter) [](https://packagist.org/packages/clarkwinkelmann/flarum-ext-typewriter) [](https://www.paypal.me/clarkwinkelmann)
Their website documents all the available options to customize a badge image https://shields.io/
