[Enhancement] Font options

[y124]

So far i am loving this tool! Just writing to ask if you could add a San-serif typeface such as Roboto or Ubuntu or a font selector as an option, I may try myself but I've never used PyQT5 and i am unfamiliar with the codebase.

[plu5]

Thanks for this issue! It looks like when I was implementing the ability to change font size I hard-coded the font and forgot to change it.

https://github.com/plu5/retype/blob/2c7af6a16752b56fdf56b47e4fd8b1326e4efaf5/retype/ui/book_view.py#L31

I will add an option to the settings as soon as I can!

[y124]

alright, thanks so much!

[plu5]

Finished implementing this and it is part of release 1.1.0