feat(notifications): add pull to refresh if notifications is empty

[lex111]

This may not be entirely customary, if we do not have elements, then pull-to-refresh should not be, but in my opinion this will be a nice addition.

Also, I even aligned the message "receiving notifications" in the center, so it seems to me better. Although it was required to determine the height (saveContentBlockHeight) and to set the height for the blocks to align, there may be a way to do without it, but I did not find.

Demo:

[housseindjirdeh]

This is such a great touch, I think it looks so much better in the center and I can't see why we shouldn't be able to pull to refresh when there's no items!

Thanks a million matey, it looks solid 🎉