Add a json schema for apidump json output

[KarenGhavam-lunarG]

I'd recommend adding some form of format version declaration, so applications can easily detect how the format evolves over time. (In json-schema, that versioning is accomplished using a "$schema" element) I'd also recommend defining some sort of comment element, since json does not support commenting (It's really handy to make data inert without being forced to delete it from the document)

This is an all-values-are-strings design. json-schema provides json-native types, from which producer/consumer code can be generated, and most importantly, can validate json documents against the schema (useful for detecting the error above) independently of any application code.

FYI the json-schema defined for the Device Simulation layer directly implements Vulkan datastructures (when possible; there are some C-isms that dont map directly to json types) See https://schema.khronos.org/vulkan/devsim_1_0_0.json