add JSON node should match context

[badaz]

Hi,

First, thanks for your work. I was looking for a way to check that a json node matched a pattern and only found the "JSON should be valid according to this schema" way which seemed a little overkill when you only want to test one JSON node. So this should be used to test a single node against a regex.

[badaz]

Done

[sanpii]

Merged, thank you 😃