✨ Add AB test block

Closes #449

packages/schemas/features/items/enums.ts

@@ -1,4 +1,5 @@
 export enum ItemType {
   BUTTON,
   CONDITION,
+  AB_TEST,
 }

packages/schemas/features/items/schemas.ts

@@ -1,7 +1,11 @@
 import { z } from 'zod'
 import { buttonItemSchema } from '../blocks/inputs/choice'
 import { conditionItemSchema } from '../blocks/logic/condition'
+import { aItemSchema, bItemSchema } from '../blocks'
 
-const itemSchema = buttonItemSchema.or(conditionItemSchema)
+const itemSchema = buttonItemSchema
+  .or(conditionItemSchema)
+  .or(aItemSchema)
+  .or(bItemSchema)
 
 export type Item = z.infer<typeof itemSchema>