Add Ukrainian (uk) translation of the documentation

[WER-CORE]

Description

This PR adds a complete Ukrainian (uk/) translation of the CmlLib.Core documentation from the English version.

What's included

• Complete documentation translation (64 files):
  • CmlLib.Core (Getting Started, Login and Sessions, Mod Installers, More APIs, Utilities, Resources)
  • Auth.Microsoft (CmlLib.Core.Auth.Microsoft, XboxAuthNet.Game, XboxAuthNet.Game.Msal, Bedrock Auth)
  • MojangAPI (Endpoints, Security Questions)
  • Installer.Forge & Installer.NeoForge
  • ...
• MkDocs configuration:
  • Added mkdocs.uk.yml with Ukrainian locale and navigation support.
• Code snippets & Comments:
  • All C# code samples, terminal commands, and configuration examples are preserved with translated comments for clarity.
• Structure & Links:
  • Full parity with the English documentation structure.
  • All relative links, headings, anchor IDs, and API references have been carefully verified.

Verification

• Tested locally with mkdocs build -f mkdocs.uk.yml — builds cleanly with 0 errors and 0 warnings.
• Verified navigation and theme rendering in Material for MkDocs.