Summary:
Changes RNTester, first attempt in the direction of improving the RNTester overall. Related ticket: #24647
Changed the `js` directory of the RNTester to have the following structure:
```
- js
- assets
- components
- examples
- types
- utils
```
* **assets**
_Any images, gifs, and media content_
* **components**
_All shared components_
* **examples**
_Example View/Components to be rendered by the App_
* **types**
_Shared flow types_
* **utils**
_Shared utilities_
## Changelog
[General] [Changed] - Update folder structure of RNTester's JS directory.
Pull Request resolved: https://github.com/facebook/react-native/pull/25013
Differential Revision: D15515773
Pulled By: cpojer
fbshipit-source-id: 0e4b6386127f338dca0ffe8c237073be53a9e221
3945f10561
