Added scroll pagination mode

[yamila-moreno]

Hi there, as we talked in #280 , this PR adds pagination scroll mode. To enable it, just add in your params the setting scrollPagination (you can see an example in the exampleSite/config.toml).

When enabled, the blog loads a different pagination with a javascript (this snippet was taken from the hugo discourse).

I hope you like it! Any feedback to improve it is very welcome :)

[kakawait]

@yamila-moreno thank you for contribution I will check that asap. But for what I see should be good.