I unconsciously reach for ripgrep on a daily basis. Finding references just is incredibly easy without cluttering it with stuff listed in .gitignore (I'm looking at you node_modules..)
This has reminded and motivated me to submit a donation to the project.
As of now, you can't. While I believe the various efforts that are being undertaken to help fund FOSS are extremely important, they aren't a good fit for me. ripgrep is and I hope will remain a project of love that I develop in my free time. As such, involving money---even in the form of donations given without expectations---would severely change that dynamic for me personally.
Instead, I'd recommend donating to something else that is doing work that you find meaningful. If you would like suggestions, then my favorites are:
This has reminded and motivated me to submit a donation to the project.