Add Keycloak guide

[Sherex]

Hello,

I created this guide for Keycloak a while ago (I didn't realise there was a docs repo) and posted it as a gist here and on the feature tracker.

I added the image tag at the bottom for a Keycloak logo pointing to https://static.requarks.io/logo/keycloak.svg, let me know if I should remove it. :)

[chikamichi]

Terrific! I'd suggest adding a link to the guide though, maybe on https://github.com/Requarks/wiki-docs/blob/master/auth.md 🤷 (there is this unlinked Generic OpenID / Oauth2 item in the Modules list, which could be a good candidate; or adding an item altogether such as Keycloak OpenID Connect).

[Sherex]

Ah that's probably smart :P

I added it as it's own section as there are some very specific points that are for Keycloak.
But I created a generic one too here: #30

Let me know if something should be changed :)

[chikamichi]

Hopefully NGPixel will come by and validate some pending PR soon (or delegate to someone else?) :)

[chikamichi]

Thanks! Both of you :) 🙏