SlackBuildsOrg/system/nano-syntax-highlighting

nano-syntax-highlighting (Improved Nano Syntax Highlighting Files)

This repository holds {lang}.nanorc files that have improved
definitions of syntax highlighting for various languages.

Once there you should add the languages you want to your nano
configuration file ~/.nanorc or /etc/nanorc, for example:

## C/C++
include "/usr/share/nano-syntax-highlighting/c.nanorc"

Or to be less verbose, append content of the folder in one line
with wildcard:

For current user.
$ echo 'include "/usr/share/nano-syntax-highlighting/*.nanorc"' >> ~/.nanorc

For all users.
# echo 'include "/usr/share/nano-syntax-highlighting/*.nanorc"' >> /etc/nanorc