Write docs on npm scripts

- npx
- .bin
- use package.json
-`pre` / `post`
- concurrently
- rm -rf
- `npm test`
- `npm start`
- `npm run `

Start by locating the repository's documentation structure and the existing material about package.json and npm commands. Explain the listed topics, including npx, .bin, pre/post scripts, concurrently, rm -rf, npm test, npm start, and npm run ; done means the documentation covers these npm-script concepts clearly.

Written by the indexing model from the issue text.