Add benchmarking

[brandon-leapyear]

We should check benchmarking against other methods of doing the same thing, specifically:

• aeson-schemas
• manual FromJSON instance
• manual FromJSON instance using genericFromJSON
• FromJSON generic deriving

The following items should be benchmarked:

• Compile time of schema/data type definition
• Compile time of call sites (extracting fields from schema/data type)
• Run time