Documentation: Map editor

[davidbmaier]

Probably deserves its own category under Create.

Details:

• A brief overview of the different editor types
• A basic introduction to the general navigation in the editor
• Move over content from https://wiki.trackmania.io/en/content-creation/map-editor and its subpages

There's obviously tons of stuff that can be documented here, but getting the initial structure done is the first goal.