Implement native method to create notification channel

Summary: This differential implements native method to create android notification channel, updates JavaScript type and uses it JavaSCript code.

Test Plan:
Since API level 26 all notifications must be assigned to a channel: https://developer.android.com/develop/ui/views/notifications/channels, I presume that simply ensuriing notifications are
delivered both in the foreground and background is enough to test this differential.

Reviewers: tomek, bartek

Reviewed By: tomek

Subscribers: ashoat, atul

Differential Revision: https://phab.comm.dev/D6377