docs(oidc): web keys (#8508)

# Which Problems Are Solved

Explain the web key implementation and usage in zitadel.

# How the Problems Are Solved

Add documentation

# Additional Changes

- none

# Additional Context

- Related to https://github.com/zitadel/zitadel/issues/7809
- Example cURL commands are broken:
https://github.com/zitadel/zitadel/issues/8507

---------

Co-authored-by: Livio Spring <livio.a@gmail.com>

docs/sidebars.js

@@ -230,6 +230,8 @@ module.exports = {
                 "guides/integrate/login/oidc/oauth-recommended-flows",
                 "guides/integrate/login/oidc/device-authorization",
                 "guides/integrate/login/oidc/logout",
+                "guides/integrate/login/oidc/webkeys",
+
               ],
             },
             "guides/integrate/login/saml",