Added device event subscription

[markoImake]

Hi Eddy
I was working on my own nativescript-particle plugin until I saw you recently published this one. I added the additional features that I was using into your plugin. These include:

1. loginWithToken - this is needed for managing shadow accounts when implementing Two-Legged Authentication (https://docs.particle.io/guide/how-to-build-a-product/authentication/#two-legged-authentication)
2. isAuthenticated and accessToken methods to make it easier to manage shadow accounts
3. subscribe to (and unsubscribe from) events on a TNSParticleDevice
4. Particle Device Setup Wizard for ios, using particle 'ParticleSetup' sdk (https://github.com/particle-iot/particle-setup-ios)

[EddyVerbruggen]

Hi! This is honestly excellent work! I'm very glad you decided to merge your code with the repo. And I'd be happy yo add you as a collaborator to the repo if you want to.

I've asked 2 questions, please check them out when you have time.

I'd be happy to test the updated demo app and add docs for these new features.

Thanks,
Eddy

[EddyVerbruggen]

For my info: there's no device setup wizard for Android?

[markoImake]

There is a device setup wizard available for Android. The device setup library is a separate native dependency - https://github.com/particle-iot/spark-setup-android, more info here https://docs.particle.io/reference/android/#android-device-setup-library. I don't have much experience with android so wasn't comfortable attempting to add that in. I do require it for the project I'm working on though. Is this something that you will be interested in adding?

[EddyVerbruggen]

Ah, understood, fair enough! I always strive for x-platform feature parity so I might give it a stab! Not this week though, I'm swamped.

[EddyVerbruggen]

.. that being said, that's not blocking for merging this PR of course.

[markoImake]

Ok sounds good. Do I need to do anything further to get the PR merged?

[EddyVerbruggen]

Nope, this is perfect, I'll try to merge it asap.