slides can now be split with separators!

Separators

Previously it was necessary to divide pages by file name, but now it is possible to separate them using separators.

<!-- background: title -->

# Title

---

<!-- background: red -->

## Hi😜

This page is the next page of the title.

Sample Repo: https://github.com/hiroppy/fusuma/tree/master/samples/intro-with-separator

Show the development url

#16

Thanks @zhaozhiming!