🌍 i18n: Add Thai Language Support and Update Translations

[rubentalstra]

Summary

Closes: #6214
Docs: LibreChat-AI/librechat.ai#259

This pull request includes changes to add support for the Thai language in the application. The most important changes involve updating language options, localization files, and the language resource configuration.

Localization updates:

• client/src/components/Nav/SettingsTabs/General/General.tsx: Added Thai language option to the language selector.
• client/src/locales/en/translation.json: Added the Thai language entry to the English translations file.
• client/src/locales/th/translation.json: Created an empty Thai translations file.

Language resource configuration:

• client/src/locales/i18n.ts: Updated import statements and resource configuration to include Thai translations. [1] [2]
• client/src/locales/i18n.ts: Minor formatting change to the fallback language configuration.

Change Type

• New feature (non-breaking change which adds functionality)
• This change requires a documentation update
• Translation update

Testing

Please describe your test process and include instructions so that we can reproduce your test. If there are any important variables for your testing configuration, list them here.

Test Configuration:

Checklist

• My code adheres to this project's style guidelines
• I have performed a self-review of my own code
• I have commented in any complex areas of my code
• I have made pertinent documentation changes
• My changes do not introduce new warnings
• I have written tests demonstrating that my changes are effective or that my feature works
• Local unit tests pass with my changes
• Any changes dependent on mine have been merged and published in downstream modules.
• A pull request for updating the documentation has been submitted.