docs(basti-cdk): reorganize readmes

[BohdanPetryshyn]

Proposed Changes

This PR reorganizes READMEs according to the new monorepo structure. The new approach will be the following:

1. The root README.md file is going to mostly describe Basti CLI and reference Basti CDK project as the main IaC solution for Basti.
2. Basti CLI's README is going to the the root README file. I set up a git hook for keeping these two files in sync.
3. Basti CDK has it's own README file which describes all its features and explains how to use Basti CDK with Basti CLI.

Related Issue

48

Checklist

• [x] All the tests and checks passed (npm run test).
• [x] I have added necessary documentation and/or updated existing documentation.
• [x] I have added or modified tests to cover the changes.