Progress indicator API

[pascalbaljet]

This PR exposes the internal methods that we're using to drive the Progress indicator, giving developers control over the progress bar as well.

import { progress } from '@inertiajs/vue3'

progress.start()      // Begin progress animation
progress.set(0.25)    // Set to 25% complete
progress.finish()     // Complete and fade out
progress.reset()      // Reset to start
progress.remove()     // Complete and remove from DOM
progress.hide()       // Hide progress bar
progress.reveal()     // Show progress bar

progress.isStarted()  // Returns boolean
progress.getStatus()  // Returns current percentage or null

The hide() and reveal() methods use a counter system. This is used internally for prefetching.

progress.hide()    // hideCount = 1, bar hidden
progress.hide()    // hideCount = 2, bar still hidden
progress.reveal()  // hideCount = 1, bar still hidden
progress.reveal()  // hideCount = 0, bar shown

progress.reveal(true)  // Always shows regardless of hideCount