suggestion: support map or JSON values

[bjorndm]

I see that {} is now reserved. Perhaps this could be used for map or JSON values like in https://github.com/tidwall/xv? I can probably contribute a PR but I'd like to ask if you consider this an acceptable feature? The reason I ask is that I want to use this library for JSON processing. While it is possible to use JSON using the Extender, native support like in xv would help a lot.

Thanks for your consideration!