Markup links using linkify

I've added two new pub functions here, one for escape html entities that uses the marksman_escape crate and escape all html and other one to convert plain links to html links using linkify crate instead the complex regex.

This is useful to parse plain text messages and convert only links to clickable links in pango_markup. The rest of the message will be displayed correctly because combining these two function we'll have a correct pango markup always.

We can use this in Fractal to render the body, and the other one to render the formated_body.