Update branding and docs to acknowledge rename of Minetest to Luanti

[Lazerbeak12345]

As you are almost certianally aware by now, Minetest, the game engine, was recently renamed to Luanti. I waited to report this issue until the following conditions were met, as they have now been.

• The minetest.net website redirects, as does content.db, to the new domain name
• A new version of the engine with the new name applied has been released
• The luanti package files are available in my current daily driver, Artix linux (packaged through Arch Linux repos). (Significant since this is a rolling-release distro and can show the point at which the package is effectively available)

Of note is that the legacy game "Minetest Game" (provider of the default mod) did not change it's name.

It's certain that WhyNot in it's current form is a derivative of that legacy game, targeting the Luanti game engine.

Personally, I'd prefer to follow as their new landing page does and in reference to Luanti, we should refer to Luanti as "An open source voxel game engine" when relevant.

Part of this may involve renaming our organization name, as "minetest" there refers to the game engine, and it's well understood that we may be releasing Whynot for other games like Nodecore and Hades in the future.

[dacmot]

Yes I noticed the change. Very good points!