docs: contributing styles

CONTRIBUTING.md

@@ -7,3 +7,11 @@ Please submit a pull request for minor changes and submit issues for major chang
 ## Testing
 
 When providing a new feature or bug fix, please provide tests that demonstrate the issue along with your fix.
+
+## Themes
+
+New styles need to be implemented in the `styles.go`, and then `go generate
+./...` will create the JSON files from it.
+
+You can look up all references of another theme (e.g. Dracula), and add your
+theme accordingly.