I'd love to have the time. Family and work take it almost all up. Compilers, semantic models and type systems are of high interest for me and I've done some work related to those. But I'd be out of my depth. There are many more areas that could be contributed to. Hats off if he wrote the docs as well as the compiler, it's great technical writing, as an example of another area that usually needs assitance.
Nowadays, I need to pull larger-scale integrations of libraries together, and the quality of the supply chain along with productive development practice occupy my mind. I suppose I wouldn't be out of my depth to work on the Jetbrains IDE plugin.
I tend to buy licenses for tools I use (Sublime), I'd help a Patreon. If this could acquire foundation support like Rust did, it might reach a similar position.
1. "How can I help" but it's a lie.
2. Silence.