docs(gitbook): integrate GitBook documentation

[drichar]

Description

This PR integrates the use-wallet GitBook documentation into the monorepo, establishing a foundation for maintaining comprehensive and up-to-date documentation alongside the codebase. It sets up the GitHub Sync integration with GitBook and outlines the workflow for contributors to update documentation.

Details

• Created docs folder in the repository root to house all GitBook documentation
• Added initial GitBook documentation content
• Configured .gitbook.yaml for proper syncing between GitBook and GitHub
• Set up docs/gitbook branch for GitBook's GitHub Sync integration
• Added docs/** to .eslintignore and .prettierignore
• Implemented GitHub Sync integration:
  • Changes made in GitBook UI will be automatically synced to the docs/gitbook branch
  • Updates in docs/gitbook will be reflected in the deployed GitBook documentation
• Established workflow for contributors:
  • Documentation changes can be included in feature PRs to main
  • After merging to main, changes will be propagated to the docs/gitbook branch
  • This ensures all documentation updates are synced with the deployed GitBook version