Make comments italic

[rashil2000]

GNU Nano 5.5+ supports italics and bold as text attributes.

Many text editors provide ways to italicize comments, it just makes code elegant to read.

This can be added for version 5.5 and above.

[davidhcefx]

This repo is in fact a collection of lots of contributions from different authors. It's hard to make sure all 119 rcfiles add italicized comment highlighting.