Add block_quote prefix on empty lines too

[patrick91]

I notice that when a blockquote has an empty line it wouldn't be rendered properly, as it would be broken in two blockquotes, from:

> abc
> 
> abc

to

> abc

> abc

Which are rendered differently in html:

abc

abc

and:

abc

abc

[lepture]

Hi, thanks for the fix. Can you add a test case for it?

[lepture]

@patrick91 thanks for your patch. But the tests are failed. Can you have take a look at the errors?

[patrick91]

@lepture done, the tests are passing locally, I had to rstrip the last > to make it work properly 😊