feat: change the file structure

[DiogoRDuarte]

Because

• Some files add names whose purpose was not obvious. Their placement in the file structurewas, at times, not the most suitable one too. Both points apply to functions.

Refactor

• Moves the CSS inside the "assets" folder
• Changed the names of certain files to make them for descriptive (e.g. DescriptionChanger.ts)
• Moved functions into files that seem more suitable (e.g. xSetter -> NavigationKeyHandler.ts)

Tests

• Fixes semantic issues with divs inside table rows