walk-up-path

Given a path string, return a generator that walks up the path, emitting
each dirname.

So, to get a platform-portable walk up, instead of doing something like
this:

``js
for (let p = dirname(path); p;) {

// ... do stuff ...

const pp = dirname(p)
if (p === pp)
p = null
else
p = pp
}
`

Or this:

`js
for (let p = dirname(path); !isRoot(p); p = dirname(p)) {
// ... do stuff ...
}
`

You can do this:

`js
const { walkUpPath } = require('walk-up-path')
for (const p of walkUpPath(path)) {
// ... do stuff ..
}
`

API

`js
const { walkUpPath } = require('walk-up-path')
``

Give the fn a string, it'll yield all the directories walking up to the
root.