Fix HMR issues and add Vite 6 compatibility

[shekohex]

This pull request introduces compatibility with Vite 6, updates dependencies, and improves code consistency and maintainability. The most significant changes include upgrading dependencies, refactoring the plugin to align with Vite 6's API, and improving code formatting and organization.

Vite 6 Compatibility

• Updated the vite dependency to version ^6.0.0 and adjusted peer dependencies to require Vite >=6. (package.json: package.jsonL71-R78)
• Refactored the handleHotUpdate method to align with Vite 6's recommendation of returning void for async operations that don't affect modules immediately. (src/index.ts: src/index.tsL14-R90)
• Added optimizeDeps configuration in the E2E test Vite config for better dependency optimization in Vite 6. (tests/e2e/app/vite.config.ts: tests/e2e/app/vite.config.tsL20-R32)
• Updated build options in vite.config.ts to target es2020 for modern browser compatibility. (vite.config.ts: vite.config.tsL1-R45)

Dependency Updates

• Downgraded @vitejs/plugin-react from ^4.3.1 to ^4.2.1 to ensure compatibility with the updated Vite version. (package.json: package.jsonL58-R58)
• Updated vite-plugin-static-copy to version ^2.0.0 for compatibility with Vite 6. (package.json: package.jsonL71-R78)

Code Refactoring and Formatting

• Reorganized imports for better readability and consistency, switching to double quotes for all imports. (src/index.ts: [1] tests/e2e/app/vite.config.ts: [2] vite.config.ts: [3]
• Renamed the handleFileChange function to handleTranslationFileChange and extracted isFileInLangPath for improved clarity and modularity. (src/index.ts: src/index.tsL14-R90)

Documentation

• Updated the README.md to mention compatibility with Vite 6. (README.md: README.mdR22)

These changes ensure the plugin is fully compatible with Vite 6 while improving code quality and maintainability.

Closes #3

[shekohex]

@adesege please review.