Add support for classes on li-tags using <>

`*<foo> Lorem Ipsum` will now generate `<li class="foo">Lorem Ipsum</li>`. It works for both ul and ol but ol is a bit crude and the class goes after the dot, e.g. "1.<foo>" but changing would require a larger rewrite of the RE and logic.

The purpose is to be able to create todo-lists such as

    *<finished> Lorem
    *<aborted> Ipsum
    * Dot
    * Sit
    *<pending> Amet