Create release-ready documentation

[TheDuckCow]

As the title suggests, there needs to be at least basic self service documentation to accompany the public v1.0 launch. Doc pages should cover:

• General intro
• Tutorial: Creating a figure 8 road with an intersection
• Page on RoadPoints
• Page on RoadSegments
• Page on LaneSegments & AI
• Page on Intersections, with subsections on procedural & hand made models (if we adopt this strategy)

We likewise should then update the project readme to point to these documentation wiki pages.

The proposal would be to use the public wiki pages for this (but prepped in advance without publish, since these pages are not visible on the github free tier unless made open source)

[TheDuckCow]

Let's add a comment that talks about potential first time startup errors due to the .import folder not being present. As found by Bret:

The initial error generates the following console messages:
editor/editor_node.cpp:3304 - Addon 'res://addons/gut/plugin.cfg' failed to load. No directory found. Removing from enabled plugins.