Support `picture` tag for markdown pages

Hi!

Can you keep `picture` tag for a markdown pages instead of omitting it?
* Here is [the readme on pub.dev](https://pub.dev/packages/fpjs_pro_plugin/versions/1.0.4) without tag
* Here is the same [readme on GitHub](https://github.com/fingerprintjs/fingerprintjs-pro-flutter/blob/1.0.4/README.md)
* Here is the [GitHub documentation page](https://docs.github.com/en/get-started/writing-on-github/getting-started-with-writing-and-formatting-on-github/basic-writing-and-formatting-syntax#specifying-the-theme-an-image-is-shown-to) with the recommendations for using `picture` tag.