Gradually merge the declaration file "hakase" into the source codebase

[Sayakie]

ESLint does not interpret Hakase/index.d.ts, might be there is a solution to solve. But we decide deprecate the declaration and merge that into source codebase.

If

Already provided by discord.js. Should be removal in next major release.

Hakase/typings/hakase/index.d.ts

Lines 1 to 5 in 3948378

	declare type If<T extends boolean, A, B = null> = T extends true
	? A
	: T extends false
	? B
	: A | B