Function guard

guard<T>(validator): ((input) => input is T)
Turn a validator into a type guard
Type Parameters
- T
  The validated type
Parameters
- validator: Validator<T>
  The validator to convert
Returns ((input) => input is T)
- - (input): input is T
  - Parameters
    - input: unknown
    Returns input is T
Remarks
A validator makes a assertions about the input and returns a typed output. In contrast a guard is able to cast the type of the input for the rest of its block.

Example
```
if (guard(isNumber)(input)) {
    // input is treated as a number in this block
  }
```
- Defined in factories/guards.ts:22