Add JSON Path context to a parser
When parsing a complex structure, it helps to annotate (sub)parsers
with context, so that if an error occurs, you can find its location.
withObject "Person" $ \o ->
Person
<$> o .: "name" <?> Key "name"
<*> o .: "age" <?> Key "age"
(Standard methods like (.:) already do this.)
With such annotations, if an error occurs, you will get a JSON Path
location of that error.
Since 0.10