Feature request: isIn (array) or isOneOf

A useful method to check if an expression exists in an array, example:

```typescript
const fruits = ['apple', 'orange']
const vegetables = ['eggplant', 'carrot']
const food = 'apple'

const foodCatrgory = match(food)
   .isOneOf(fruits).then('fruit')
   .isOneOf(vegetables).then('vegetable')
   .else('not food')
```