Multiple uri validation

### What problem are you trying to solve?

i try to validate multiple uri in a string that separate by comma( `,` )

[I found a very similar pr](https://github.com/hapijs/joi/pull/1842)

so i expect `uri({multiple : true})` but it does not exist.

There may be other solutions but I think this is a pretty consistent feature considering `email({ multiple : true }).`

### Do you have a new or modified API suggestion to solve the problem?

```javascript
joi.string().uri()

joi.string().uri({
multiple: true,
})
```