[feature] Convert JSON5 input to JSON if set in Content-Type

[lakano]

Hi,
Thank you for your works!
Your code already include JSON5 library, but doesn't seems to permit us to write JSON5 and to converted to strict JSON for a classic 'application/json' Content-Type.
This can save us time when we manually wrote the request directly in your addon, without the need to double quote every keys for example.
Let us known if you have include this one day :)
Thank you!