Set parameters when using JWT.decode

[JHubi1]

I use the JWT.decode method quite often. I believe it is less resource intense (idk), and easier to implement, because you don't have to set all the check parameters.

One thing that's always getting on my nerves is that the function doesn't set the necessary attributes of the JWT object, which makes it harder to work with (arguably not much harder but harder nonetheless).

I'm not sure whether this is a brilliant idea or not. As far as I can tell, nothing should break, but there were no tests and I didn't want to write my own, so I couldn't really test. I added documentation though that lets devs know to use this values with caution as they are not checked.

[jonasroussel]

You are right, JWT.decode is way faster, because it doesn't have to calculate the RSA/EC.. signature.
The only thing to keep in mind is by consequence the payload (and header) could not be trusted. But works fine if you just want to see what inside the token, and there is no reason to not parse the standard fields, nice add!

I just used you PR to make some refacto to the original code, merge the PR that I created on your fork https://github.com/JHubi1/dart_jsonwebtoken/pull/1 and I can push and publish this one

[JHubi1]

Merged it

[jonasroussel]

Added in the last version: https://pub.dev/packages/dart_jsonwebtoken/versions/2.17.0

[JHubi1]

Thank you very much