Consider extracting some logic to a cljsjsify library

[kenbier]

It would be nice to not have to release a new wrapper library everytime someone wants to use a cljsjs React library.

Generating the macros could potentially be done by parsing theext.js file of the cljsjs project, then dynamically creating a namespace and the macros in that namespace. This would also allow app authors to generate wrappers at compile time, based on the cljsjs version they are using.

Haven't had time to look into the edge cases of this.