Rework README.md

[arcayr]

Basically copy-pasting what I said to you earlier.

The current README.md is very HN-blogspam or Medium Thinkpiece™-esque. It feels like it suffered from Kubernetes documentation syndrome, where only people who are already in the know will understand what it does and how it works.

The entire BG section could be shifted into a blog post or lower down in the file, because it still doesn't explain what the project is in its current state right now.

You described it in Discord as "basically think JVM for wasm." That explained the project in five words more than I could get out of the README atm.