Implement Google in app update api

[AjeshRPai]

Implement the Google in app update api in the app.

### Tasks
- [ ] Check for app updates
- [ ] If a flexible update is available, then show an update available option. On clicking update, trigger flexible update 
- [ ] If an immediate update option is available, trigger immediate update

[peril-wordpress-mobile]

	Fails
🚫	Please add a type label to this issue. e.g. '[Type] Enhancement'

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[dangermattic]

Thanks for reporting! 👍