[New Library] Android NotificationChannel extensions

[EdricChan03]

I've noticed that the NotificationChannel class has some rather... interesting naming conventions for getters/setters of boolean properties:

/**
 * Sets whether notifications posted to this channel should display notification lights,
 * on devices that support that feature.
 *
 * Only modifiable before the channel is submitted to
 * {@link NotificationManager#createNotificationChannel(NotificationChannel)}.
 */
public void enableLights(boolean lights) {
    this.mLights = lights;
}

/**
 * Returns whether notifications posted to this channel trigger notification lights.
 */
public boolean shouldShowLights() {
    return mLights;
}

As a result, no synthetic Kotlin mutable properties are generated, resulting in having to use the Java getter/setter methods respectively.

Proposed extensions

• isBadgesShown: delegates to setShowBadge (setter)/canShowBadge (getter)
• isBubblesAllowed: delegates to setAllowBubbles (setter)/canBubble (getter)
• isDndBypassable: delegates to setBypassDnd (setter)/canBypassDnd (getter)
• isVibrationEnabled: delegates to enableVibration (setter)/shouldVibrate (getter)
• isLightsEnabled: delegates to enableLights (setter)/shouldShowLights (getter)

(API names are currently tentative, the names will change as further experimentation is done)

Additional tasks

• Add notice that the properties can't be modified once they have been submitted (perhaps a Kotlin opt-in annotation, something like ImmutableAfterCreation)