Function relative

relative(base: string, target: string, charCompare?: CharCompare): null | string
Returns the relative path from base to source, or null if not a subpath
Parameters
- base: string
  The base path
- target: string
  The target path
- OptionalcharCompare: CharCompare
  Optional custom code point comparison function
Returns null | string
The relative normalized path, or null if not a subpath
Remarks
- This function uses matches for subpath matching
- Unlike standard implementations, this functions returns null when target is not a direct subpath of base
Example
```
relative('foo/bar', 'foo/bar/baz') // returns 'baz'
relative('baz', 'foo/bar') // returns null
```