Feat/reworked language codes (#865)

* Reworked language codes to use Steam localization standards

* Reworked language codes tweaks (#864)

* Language code rework tweaks

* Update bg.lua

* Reevaluate whether a language is WIP

* Update bg.lua

* Even better mark for languages as WIP (> 80% translated)

* Update zh_cn.lua

* Update cs.lua

* Fix for game language codes

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Co-authored-by: kittenchilly <mario.pikmin.zelda@gmail.com>

features/eid_mcm.lua

@@ -336,7 +336,7 @@ if MCMLoaded then
 				end
 				renderDummyDesc(true)
 			end,
-			Info = {"Changes the language.","Languages marked as WIP are incomplete."}
+			Info = {"Changes the language.","Languages marked as WIP are incomplete. Contributions welcome!"}
 		}
 	)
 	-- Item Name Language