fix(types): Add undefined return type in onMutate (#2089)

* onMutate callback add void in return type

* Add core type

* return type void to undefined

* onMutate return type change 'Promise<TContext> | Promise<undefined> | TContext | undefined'

Author: eomttt

src/core/types.ts

@@ -474,7 +474,7 @@ export interface MutationOptions<
   mutationFn?: MutationFunction<TData, TVariables>
   mutationKey?: MutationKey
   variables?: TVariables
-  onMutate?: (variables: TVariables) => Promise<TContext> | TContext
+  onMutate?: (variables: TVariables) => Promise<TContext> | Promise<undefined> | TContext | undefined
   onSuccess?: (
     data: TData,
     variables: TVariables,

src/react/types.ts

@@ -75,7 +75,7 @@ export interface UseMutationOptions<
   TContext = unknown
 > {
   mutationKey?: string | unknown[]
-  onMutate?: (variables: TVariables) => Promise<TContext> | TContext
+  onMutate?: (variables: TVariables) => Promise<TContext> | Promise<undefined> | TContext | undefined
   onSuccess?: (
     data: TData,
     variables: TVariables,