Rewrite of the files and folders section

[ferafiks]

Motivation

The files and folders section is quite outdated and is lacking a lot of useful information. On top of that, the name of the section is quite misleading, implying to be about IO operations.

Additionally, there are other very minor sections that could be merged with files and folders into one, removing clutter from the sidebar.

Description

This PR:

1. Merges "files and folders", "Nuget" and "Extensibility" sections into one, called "Project"
2. Rewrites the majority of pages under those sections
3. Adds a new sub-section "packages" that goes into detail how they work and how to work with them

TODO

• Rewrite existing pages under Files and folders
• Add package pages
• Rewrite "distribute a game"
• Rewrite existing pages under Nuget
• Rewrite existing pages under Extensibility
• Rewrite "distribute a game"
• Create visualizations