Allow id of notifications to be specified

[steppy452]

I'm submitting a...

[ ] Regression (a behavior that used to work and stopped working in a new release)
[ ] Bug report  
[ ] Performance issue
[x] Feature request
[ ] Documentation issue or request
[ ] Other... Please describe:

Current behavior

Notification ids are currently kept track internally and have no way of being retrieved for clearNotification callback in notifications hook to be used.

Expected behavior

Proposing ability to pass an optional id parameter when creating notifications which can later be used to clear specific notification (or even notification group, if the same id is used for multiple notification). We'll still want to keep the current internal id to ensure uniqueness

Minimal reproduction of the problem with instructions

What is the motivation / use case for changing the behavior?

Necessary for manual clearing of specific notification(s) which isn't coming directly from using the "close" button on the notification

Environment

Libs:
- react version: X.Y.Z
- reablocks version: X.Y.Z


Browser:
- [ ] Chrome (desktop) version XX
- [ ] Chrome (Android) version XX
- [ ] Chrome (iOS) version XX
- [ ] Firefox version XX
- [ ] Safari (desktop) version XX
- [ ] Safari (iOS) version XX
- [ ] IE version XX
- [ ] Edge version XX
 
For Tooling issues:
- Node version: XX  
- Platform:  

Others: