feat(components): include StateContent in components barrel

Author: michael-xd

src/components/index.ts

@@ -1,5 +1,5 @@
 import { Request } from './request';
-import { StateEmpty, StateError, StateLoading } from './states';
+import { StateContent, StateEmpty, StateError, StateLoading } from './states';
 
 export * from './request';
 export * from './states';
@@ -8,5 +8,6 @@ export const COMPONENTS = [
   Request,
   StateLoading,
   StateEmpty,
-  StateError
+  StateError,
+  StateContent
 ];