Add aliases

[TorbenKoehn]

An alias should look like this

alias alias-name <element>

e.g.

alias btn a.btn(href=$url)

This can then be used like a regular element tag

btn.btn-default(href='/some/sub/page')

The calling element will
Notice that both href-attributes will be merged and create a single, complete URL.

[jacmoe]

👍