Feat/side by side

[Kamilcuk]

This Pull Request fixes/closes #1294.

It changes the following:

• FEATURE: Side-by-Side Diff Mode: Adds a lateral view for comparing changes, providing a clear visual distinction between
  additions and deletions.
• SHORTCUT: Toggle Key: Mapped m as the default key to switch between Unified and Side-by-Side modes.
• UI: Panel Consistency: Implements full-width selection highlighting and alignment for the side-by-side columns, including
  support for line-break symbols (¶).

I followed the checklist:

• I added unittests
• I ran make check without errors
• I tested the overall applicatio
• I added an appropriate item to the changelog