Collect pointers to upstream docs (new and changed) relevant for RHCL 1.2

Extensions

• https://github.com/Kuadrant/kuadrant-operator/blob/main/doc/overviews/extension-sdk.md 
• https://github.com/Kuadrant/kuadrant-operator/tree/main/doc/extensions 
• https://github.com/Kuadrant/kuadrant-operator/blob/main/doc/user-guides/planpolicy/plan-based-rate-limiting.md 
• https://github.com/Kuadrant/kuadrant-operator/blob/main/doc/overviews/telemetrypolicy.md

coming: https://github.com/Kuadrant/kuadrant-operator/pull/1624 

DNS 

• https://github.com/Kuadrant/kuadrant-operator/blob/main/doc/user-guides/dns/core-dns.md [Updated]
• https://github.com/Kuadrant/kuadrant-operator/blob/main/doc/user-guides/dns/understanding_dns_delegation.md [Added]
• https://github.com/Kuadrant/kuadrant-operator/blob/main/doc/reference/dnspolicy.md [Updated]

Token rate limiting

• https://docs.kuadrant.io/1.3.x/kuadrant-operator/doc/overviews/token-rate-limiting/
• https://docs.kuadrant.io/1.3.x/kuadrant-operator/doc/user-guides/tokenratelimitpolicy/authenticated-token-ratelimiting-tutorial/
• https://kuadrant.io/blog/token-rate-limiting/