Add alternative type name (#1199)

Author: alexpalombaro

readme.md

@@ -336,6 +336,7 @@ Click the type names for complete docs.
 - `PickByTypes` - See [`ConditionalPick`](source/conditional-pick.d.ts)
 - `HomomorphicOmit` - See [`Except`](source/except.d.ts)
 - `IfAny`, `IfNever`, `If*` - See [`If`](source/if.d.ts)
+- `MaybePromise` - See [`Promisable`](source/promisable.d.ts)
 
 ## Tips