Function to generate relative URL paths

getRelativePath.ts

function getRelativePath(location: Location, relativePath: string) {
  const base = new URL(`http://dummy${location.pathname}${location.search}`)
  const relative = new URL(relativePath, base)
  return `${relative.pathname}${relative.search}`
}

// path = /parent/child/?a=1
const location = useLocation()
const relative = getRelativePath(location, '..?b=2') 
// relative = /parent/?b=2

/*
`.` always refers to *current folder* and `..` refers to *parent folder*
```
/a/b/c/  . = /a/b/c/   .. = /a/b/
/a/b/c   . = /a/b/     .. = /a/
/a/b/c   ./d = /a/b/d  ../d = /a/d
```
It even handles search params properly. If you provide them, it will 
overwrite existing search for current location.
*/