Add support for additionalParameters when refreshing token using withFreshTokensPerformAction:

[CraigLn]

Hello,

There doesn't seem to be a way to supply additional parameter when refreshing tokens using the recommended [OIDAuthState withFreshTokensPerformAction:] method.

Currently the manual way to achieve this is to obtain a request with [OIDAuthState tokenRefreshRequestWithAdditionalParameters:], perform the request with [OIDAuthorizationService performTokenRequest:callback:], and then update the auth state with [OIDAuthState updateWithTokenResponse:].

Doing this seems to go against the documentation to use [OIDAuthState withFreshTokensPerformAction:] to refresh tokens. I just wasn't sure if there was a reason to not include a method capable of performing this action in the more preferred way.

I've taken a stab at the functionality inside this PR: #49

[CraigLn]

Forgot to mention in the initial comment that this feature currently exists inside of Android, and is solved in the same manner.

[WilliamDenniss]

Agree, let's fix this the same way as Android. Have commented in your PR.

[WilliamDenniss]

Resolved by e6acfd9.