fix(android): prevent unnecessary channelId warning

[garymathews]

• Prevent unnecessary default notification channel warning in logs.
• Add missing channelId in docs.

TEST CASE

const channel = Ti.Android.NotificationManager.createNotificationChannel({
    id: 'my_channel',
    name: 'TEST CHANNEL',
    importance: Ti.Android.IMPORTANCE_DEFAULT
});
const notification = Ti.Android.createNotification({
    icon: Ti.Android.R.drawable.ic_dialog_info,
    contentTitle: 'TITLE',
    contentText : 'This is a test',
    channelId: channel.getId()
});

Ti.Android.NotificationManager.notify(100, notification);

• Should not see this warning in logs:

Falling back to default notification channel.

JIRA Ticket

[build]

	Messages
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📖	✅ All tests are passing Nice one! All 6626 tests are passing. (There are 699 skipped tests not included in that total)

Generated by 🚫 dangerJS against fc1983b

[jquick-axway]

CR: Pass

[ssjsamir]

FR Passed: No longer get the above log message when using a custom channel.

Environment

MacOS Catalina: 10.15.1 beta
Xcode: 11.3
Java Version: 1.8.0_131
Android NDK: 18.1.5063045
Node.js: 10.16.3
""NPM":"5.0.0-1","CLI":"8.0.0-master.10""
Pixel xl (7.1.1) Emulator