Document the development environment setup for new developers

[rakeshJn]

Rough steps:

Install node (npm)
Follow the steps in fe/Readme.md
Create python virtual env
Provide config in my.env and source it (or export the entries as env variables)
Follow the steps in be/Readme.md

If running both in VSCode, in one terminal start be:
lakevision/be/app fastapi run api.py
In another terminal in VSCode:
lakevision/fe/npm run dev

Try your browser on where npm is listening, for eg: http://localhost:5173

If need a catalog, use the one from dev/docker_compose.