Paypal donations link

[Morzilla]

Hi! OpenBoard is a fantastic project, but lacks some features (like the auto-correction confidence) that you have now implemented in your fork... I'd like to make a donation, but I cannot see any paypal link... feel free to add in in the project description, I (and I think other people) want you to continue this fantastic work, beacuse as far as I know, this is the best open keyboard out there! Thanks again for your work!