Add Cartesi Rollups and Cartesi Emulator

[felipeargento]

Hello!

Just randomly came across this repo and really like what you're doing. Resources aggregators are a must in an industry that grows this fast.

I took the liberty to add a few resources about the project I contribute to.
We're an optimistic application specific rollup on top of Ethereum. And we have a custom risc-v based VM.

So I added three things:
Our rollups repo: https://github.com/cartesi/rollups
Our machine repo: https://github.com/cartesi/machine-emulator
And an application specific article: https://medium.com/cartesi/application-specific-rollups-e12ed5d9de01

If you want to learn a bit more about the project, to verify its legitimacy, here is the link:
https://cartesi.io/

Thank you for what you're doing!