feat: add language selector component to header

[Ang-m4]

Language Selector Implementation

Description

This pull request proposes a new LanguageSelector component that enables users to change the site language using a paragon dropdown.

Features

• Responsive design that shows:
  • Only the language icon on small screens (< 576px)
  • Language code (e.g., "EN") on medium screens (576px-767px)
  • Full language name (e.g., "English") on large screens (≥ 768px)
• Configurable through platform settings

Changes

• LanguageSelector.jsx: Main component implementation
• LanguageSelector.scss: Styling with media queries
• LanguageSelector.test.jsx: Testing logic for the component
• index.js: Export file for the component

Integration

The component is integrated into both header types:

• Added to LearningHeader.jsx for the learning experience
• Added to HeaderBody.jsx for Studio

Both implementations are conditional based on the ENABLE_HEADER_LANG_SELECTOR configuration flag, making it easy to enable/disable.

Related Work

This implementation relies entirely on the proposed LanguageManagement feature. For more details, please refer to the related pull request: Language Management PR.

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[Ang-m4]

Hey @dcoa! 😊 I built on your changes from your PR and would love for you to take a look when you have a chance. Let me know what you think! Thanks!

[e0d]

@Ang-m4 I've added you to the openedx-triage team as you are covered under an entity CLA. This will mean that tests will run automatically when you submit a pull request in the future. Please look for an invitation in your email and accept it.

[codecov]

Codecov Report

Attention: Patch coverage is 95.45455% with 1 line in your changes missing coverage. Please review.

Project coverage is 70.04%. Comparing base (8ef3a27) to head (48a1e4e).
Report is 2 commits behind head on master.

Files with missing lines	Patch %	Lines
src/language-selector/LanguageSelector.jsx	95.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #586      +/-   ##
==========================================
+ Coverage   68.75%   70.04%   +1.29%     
==========================================
  Files          48       49       +1     
  Lines         432      454      +22     
  Branches       97      102       +5     
==========================================
+ Hits          297      318      +21     
- Misses        132      133       +1     
  Partials        3        3              

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[e0d]

@Ang-m4 I notice there are some commit-lint failures. Please note that we use conventional commits across Open edX projects. You can read about the details here. Can you please amend your commit messages to follow our standard?

[Ang-m4]

@Ang-m4 I notice there are some commit-lint failures. Please note that we use conventional commits across Open edX projects. You can read about the details here. Can you please amend your commit messages to follow our standard?

Hi @e0d, thanks for catching that! Looks like I added an extra "s" to "style"... I'll go ahead and update the commit messages to follow the convention. Appreciate the heads-up!.