Add the option to clear multiple notifications wit the same tag pattern

[shiloSaadon]

In apps like "WhatsApp" when you enter specific chat they clear all the notifications from that specific chat, now you can achieve this using the package by creating tag that contains the group id + uuid and simply clear all the notifications that contains the group id

[Wes1324]

Thanks a lot for taking the time to make this PR @shiloSaadon. I really appreciate it.

I've just made a few minor suggestions, mainly to make the documentation slightly clearer.

Also, have you managed to test this on both iOS and Android?

[Wes1324]

Minor but I think this needs a hyphen at the start too

[Wes1324]

Suggested change

	const notificationTag: string = someGroupId + "_" + messageUUid;
	const notificationTag: string = someGroupId + "_" + messageUuid;

[Wes1324]

Suggested change

	In case you want to clear "group" of notifications you can use `clearAppNotificationsByTagThatContains`
	If you want to clear a "group" of notifications you can use `clearAppNotificationsByTagThatContains`

[Wes1324]

Suggested change

	That option allows you to create grouped notifications by sending notification with `tag` / `apns-collapse-id` that contains specific pattern and than clean all of them at once
	This feature lets you group notifications by using a `tag` (on Android) or `apns-collapse-id` (on iOS) with a specific pattern. Later, you can use that same pattern to clear all notifications in the group at once.

[Wes1324]

Suggested change

	/// Clears all push notifications that have been received by your Flutter app that container the specified pattern in their [tag].
	/// Clears all push notifications that have been received by your Flutter app that contain the specified pattern in their [tag].

[Wes1324]

I think this should be 3.1.0, and the version in the CHANELOG updated too.