[Rewrite] Implement all existing features

[Builditluc]

Linked Issues:

• https://github.com/Builditluc/wiki-tui/issues/216
• https://github.com/Builditluc/wiki-tui/issues/220

This PR is also linked to the first PR (#226).

In this PR, I aim to reimplement all existing features for wiki-tui.

TODO

• [x] ToC (Table of Contents)
• [x] Links
  • [x] link selection
  • [x] link opening
• [x] Scrolling
  • [x] prevent Scrollover
  • [x] existing vim-motions for scrolling (G, gg, ctrl-d, ctrl-u)
• [x] Search
  • [x] continue the search
  • [x] handle errors (no results, suggestions for another query)
• [x] Language
  • [x] switch search language (F2)
  • [x] switch page language (F3)
• [x] Status Bar
  • [x] show current language / other languages
  • [x] show article name
• [ ] Configuration
• [x] Popups
  • [x] Confirmation popups (changing language, etc.)
  • [x] Error popups (error when opening a page, etc.)

    Note: Configuration will be last, because I want to finish implementing the features first