Igor procedure syntax highlighting on GitHub

Dear all,
I saw in this post (http://www.igorexchange.com/node/6013) and several other posts on IgorExchange about the using GitHub for development.
I started to use GitHub but mostly I write code online (GitHub editor) when I am moving around and not having real data to test it.

In such case the syntax highlight does not work.
Do I need special directives or files for syntax highlighting to work.
Any suggestions from GitHub users.

Thank you.