Typescript Project Scaffold : Build Process

### Describe the feature

Once the initial project is created and the project grows, having the build files to be part of the folder when you run "npm run build" may confuse the folder structure and to simplify this and to have only build files that can be copied instead the whole project would simplify for further development and any pipeline integrations as well.

### Use Case

############ Before ################
npm run build

folder -a/
- a.ts
- a.d.ts
- a.js

############ After #################
npm run build

folder -a/
- a.ts
build/
- folder -a/
- a.d.ts
- a.js

### Proposed Solution

_No response_

### Other Information

_No response_

### Acknowledgements

- [X] I may be able to implement this feature request
- [ ] This feature might incur a breaking change

### CDK version used

2.61.1 (build d319d9c)

### Environment details (OS name and version, etc.)

Mac OS Ventura

Start by tracing the existing `npm run build` entry point in the TypeScript project scaffold and inspect where its generated `.js` and `.d.ts` files are written. Done means the source folder retains the `.ts` files while copied build output is grouped under `build/` for later development and pipeline integration.

Written by the indexing model from the issue text.