Add a page break block

[virgile-dev]

Is your feature request related to a problem? Please describe.
As you are working with export users want to decide where the page break happens.

Describe the solution you'd like
I'd like to have a type of block that act as a page break. When the document is exported a new page is created right after the page break block.
It should be visible on the editor so that its position can be changed and be easily deleted.

[YousefED]

close by #1372