FR: Add donate button

[ketumbra]

Make it easier for supportive individuals to donate and assist the cause
e.g.

• https://www.paypal.com/donate/buttons
• https://donorbox.org/nonprofit-blog/donate-now-button-for-nonprofits

[SoufianEly]

@ketumbra @cookiemonster maybe we can do something similar to DIVD: https://www.divd.nl/contribute/#donate
Would be good