Fix: Correct manifest file extension in README

The README currently refers to `manifest.js` in the section about limiting permissions in production. However, the boilerplate uses `manifest.ts` as the source for generating `manifest.json`. <!-- Note: Please ensure your PR is targeting the `dev` branch --> <!-- Describe what this PR is for in the title. --> > `*` denotes required fields ## Priority* - [ ] High: This PR needs to be merged first, before other tasks. - [ ] Medium: This PR should be merged quickly to prevent conflicts due to common changes. (default) - [x] Low: This PR does not affect other tasks, so it can be merged later. ## Purpose of the PR* The wrong manifest file was mentioned in the ReadMe.md file ## Changes* ReadMe.md ## How to check the feature <!-- Describe how to check the feature in detail --> <!-- If there are any visual changes, please attach a screenshot for easy identification. --> ## Reference <!-- Any helpful information for understanding the PR. -->