JSON summary of Wuffs' public API

> would it be feasible for the wuffs compiler to generate a JSON (or some other format) file with information about exported symbols and their names in the c output? then people could write programs to automatically generate wrappers around the c bindings for their language of choice, possibly even recreating things like struct methods if the language allows. this is essentially the approach taken by sokol, with the difference that sokol is written in c and so the JSON data is automatically generated via clang

Spun out of https://github.com/google/wuffs/issues/38#issuecomment-4207816984