Re-read the READMEs

[akauppi]

After a long rework, the READMEs need a check.

[akauppi]

Main readme done.

• [ ] packages/app
• [ ] packages/backend
• [ ] /{Questions|APPROACH|TRACK|SECURITY}.md
• [ ] DEVS/*.md
• [ ] anything worth keeping in: ops/old/*.md

[akauppi]

yup