Introduce RFCs and ADRs

[MgenGlder]

Description

Add folders and set up a process for larger changes to the repo based on existing RFC and ADR practices in the open source community.

[MgenGlder]

I've been thinking a bit about how this can work. I can think it can start as simply as a new folder in the repo where can put ADRs and RFCs.

We should also decide if we want to use ADRs and RFCs or both. I'll take some time to think about this.