To add support for something like Adobe extendscript, (which does not work for Dw extensions) you would also have to create the syntax checking and code hinting, as it would be adding something that is not already included in the supported code types. It is very similar to js but does contain a large number of non-standard js functions and syntax.
Your best course of action to add these would be to create a Brackets extension, and then convert the extension to work in Dw's implementation of Brackets, as they are not 100% compatible at the moments, plus unfortunatly there is no documentation for doing so.