Atom is an open source editor developed by Github. One of its useful features is ability to preview the markdown files while editing them. The Kamailio source tree includes a few such markdown files (e.g., README.md in the root folder). They are nicely displayed when browsing the GIT repository at github.com.
Another feature would be auto-completion suggestion based on the content of the edited file, so, for example, if you define a route block, then its name appears when adding the statement to execute that route.
A syntax highlighting package for kamailio.cfg has been made available at: