Add Keycloak support and example

[salyh]

Prerequisites

Please answer the following questions for yourself before submitting an issue.

• This is a feature request only 💡
• I am running the latest version
• I checked the documentation
• I checked to make sure that this feature has NOT already been requested

Is your feature request related to a problem? Please describe.
I want to use the powerful features of react auth kit together with keycloak in a seamless manner.
I did not find any example or information on wether this is supported and/or how to do it

Why are you requesting this feature
Keycloak (and auth0) ae by far the most used auth providers

Describe the solution you'd like
Documentation including an example how to use keycloak together with react auth kit.
If it is not possible yet then I would like to see an implementation/dedicated support for that

Describe alternatives you've considered
Do it manually but this is error prone

License

MIT © React Auth Kit