Joint development of open source software

Hello, Habravchane! I bring to your judgment an idea that may seem interesting (or maybe not). I myself am an open source user. Sometimes I miss some little things - hang a button, add a new section to the program ... Open source software is great that there is such an opportunity, but, as always happens, there is no time. It is easier for me to pay 50 rubles. someone for that. Of course, this amount is ridiculous, but if there are many who want it ... So the site, which will have suggestions for improvements. The client person looks for (or gets) a suitable topic and indicates how much he can pay; the human programmer finds it and says its price. When the demand / supply becomes greater than or equal to 1, the programmer starts working, at the end of which he is paid this money.
Of course, there are a lot of nuances, but I think they are all solvable.
I apologize in advance if such a service already exists, and I will be grateful if you tell me its address. (Go to Google, honestly, honestly).

PS Freelance never engaged.