Add documentation of each armor's strongness

[Megver83]

For example, in the case of Lord of the Test, there's a wiki page in Minetest wiki that enumerates its armors from weakest to strongest https://wiki.minetest.net/Games/Lord_of_the_Test/Armor#Basic_armor

Also this guy from an old mod: https://forum.minetest.net/viewtopic.php?t=3730

It doesn't need to be an exhaustive thing, just with a little ordered list in the README is enough IMO (and also including the armors from technic_armor wouldn't be a bad idea)