Add Global "Visit" Options Hook

[claudiodekker]

This PR adds a global hook that's executed prior to any visit.
This allows for modifying headers etc. in a single place, instead of having to apply them globally.

Usage

While the URL itself is only available to conditionally apply actions (e.g. on a specific path/prefix) and cannot be modified, the options object itself can be adjusted. This options object essentially reflects your Visit options (everything available from an $inertia.get('/url', options) etc.).

createInertiaApp({
  // ...
  visitOptions(options, url) {
    options.headers = {
      'some-global-header': 'some-global-header-value'
    }
  
    return options
  }
})

[sebsobseb]

@claudiodekker Nice. Is this ready to be used? Because I couldn't find it in the documentation.