[TOASTR]: Add ability to position toast in top center

[Roma36]

Issue type

I'm submitting a

• [ ] bug report
• [x] feature request

Issue description

Current behavior: Currently, NbGlobalPosition allows only to use TOP_RIGHT, TOP_LEFT, BOTTOM_RIGHT, BOTTOM_LEFT positions.

Expected behavior: NbGlobalPosition should allow to specify TOP_CENTER, BOTTOM_CENTER positions.

Other information:

Currently, it is hardly possible to extend ToastrModule due to the fact, that NbPositionHelper, NbPositionBuilderService and NbToastrContainerRegistry classes depend on the concrete enum NbGlobalLogicalPosition.

[sukeshlaghate]

Apart from Top center, bottom center it would be useful to include, middle(for placing in center of screen), left center and right center

[frankiedrake]

Just want to join to support this feature, would be very nice :)

[JustDoItSascha]

No updates on this?