Fix Getted Started documentation to reflect current state of Escoria and let a dev get up to speed quickly

[cidneyhamilton]

Please make sure you talk to the community before creating an issue.

Describe the bug
The Escoria documentation is confusingly out of date and following the instructions literally will not work.

Should clarify:

• version number needed (Godot 4 will not work with Escoria; 3.5.2 is supported)
• Directions to create an Escoria project reference the Template Library version; which is years out of date. Should direct people to clone the relevant repositories instead.
• Various typos and inconsistent references. These aren't blockers, but could easily be cleaned up.

[jnikula]

Sorry to pile on an old issue, but...

version number needed (Godot 4 will not work with Escoria; 3.5.2 is supported)

I don't think this part was actually fixed by godot-escoria/escoria-docs#71. Finding that information anywhere is still hard.

Directions to create an Escoria project reference the Template Library version; which is years out of date. Should direct people to clone the relevant repositories instead.

This is probably me being a newbie with Godot/Escoria, but the text added in commit godot-escoria/escoria-docs@650e18b didn't actually help me. Especially "copy over the addons folder" is confusing. Over to where? I'm afraid I still don't know how I should start an Escoria project.