Add metadata token endpoint property to wiki

[embesozzi]

Hello. Could you add the existing metadata parameter token_endpoint to the wiki because it's required when you implement Authorization Code Grant. Here is an example :

new Oidc.UserManager({
  ...
  metadata: {
       ...
      token_endpoint: oidcProviderDomain + '/token'
  }

It will be great if you could also add that the library supports Authorization Code Grant + PCKE according RFC7636 to the wiki , because it's good to know that the library complies with the security best practices for Native Apps RFC8252

Another suggestion is if you add that this OIDC library is Openid Certified to your wiki .

Regards.