[feat] Donate functionality

[adrianvrj]

Is your feature request related to a problem? Please describe.
Currently we are letting people vote, once the vote goal is reached, users must be able to donate to the funding.

Describe the solution you'd like
If the funding state === 3, then the user should be able to donate to the contract and the contract balance should go up as user specified.

[Iwueseiter]

Hi @adrianvrj can I quickly implement this?

[0xdevcollins]

May I pick this up?

[DanielEmmanuel1]

Can i be assigned this?