Update MAUVE's readme and citations

[krishnap25]

Hi folks,

Thank you for maintaining this excellent package!

I've just updated mauve's readme based on the following:

• the pip package outputs two new fields: mauve_star and frontier_integral_star
• add a citation to our JMLR '23 paper which advocates for this update.

The changes pass make style && make quality. Please let me know if anything else is needed and I would be happy to do so. Thank you very much!

Best, Krishna