Multiple Ligature Request

[omenos]

In addition to the ligatures from #95 , would it be possible to add the following symbols?

+=   &=   |=
-=   &^   :=
*=   &^=  --
%=   <<=

These are used in other languages such as Python and Golang, and would great to have in Hasklig! The inverse of <<=, >>=, already exists in Hasklig.

[alexlucas309]

These would be oh-so helpful. I love source code pro, but when I'm not writing Haskell I have to change font's to get ligatures, which really kills me. If these could be added, it would be doing many programmers a big favor.