feat: Add TSDoc comments

[ExE-Boss]

This adds TSDoc comments to tslib.d.ts.

The purpose of this is to make it easier to manually use these and to add whitespace lines between individual export declarations to minimise merge conflicts between my type adding PRs.

[rbuckton]

In general this is fine, but this needs to be updated with the addition of __spreadArray and the introduction of the @deprecated tag on __spread and __spreadArrays.