docs: minor updates based on feedback

[melissahenderson]

This issue is for a few minor doc updates based on feedback from Rafiki grantees.

1. Update the heading on the overview page from "Peer-to-peer payments" to "Peer-to-peer payments between ASEs" https://rafiki.dev/overview/overview/
2. Move APIs above Resources in left TOC
3. Don't lead people to believe that Docker is exclusively for dev/testing and Kubernetes is exclusively for prod. Both are options for deploying Rafiki in production, given a team's business needs.

Re 3: Max called out what Docker uses in their own docs that kind of cares for the issue. They have a section on one of their intro pages called Single host deployments. The section reads, "Compose has traditionally been focused on development and testing workflows, but with each release we're making progress on more production-oriented features."

We'd need to edit that a bit since we aren't Docker ;)