fix: export SafeActionClient type to make it portable (#267)

Includes the `SafeActionClient` into the types export to make the
inferred type of `createSafeActionClient` portable in order to avoid the
error [TS2742](https://typescript.tv/errors/#ts2742). It enables
declaring the action client in a shared package and import it in the
other apps or packages.

packages/next-safe-action/src/index.types.ts

@@ -272,3 +272,12 @@ export type InferServerError<T> = T extends
 	| SafeStateActionFn<infer ServerError, any, any, any, any, any>
 	? ServerError
 	: never;
+
+
+/**
+ * Type of the core safe action client.
+ */
+export {
+	SafeActionClient
+};
+