Document which channel adapter / gateway is Reactor friendly or not in the endpoints table

Expected Behavior
I think we should document which endpoint in the endpoints table is Reactor friendly or not. I'd like there to be a check (like a V tag, different color, or another signal) that will help users to understand if this Inbound Adapter/ Outbound Adapter/ Inbound Gateway/ Outbound Gateway has a reactive option or not. In regards to async implementations, I'm not sure if this should be classified as reactive, get mentioned in another category, or don't get mentioned at all.

Current Behavior
It's really hard to understand for example if the MqttPahoMessageHandler can interact reactively or not. The same is relevant for most of the extensions. Resolving this issue can improve Reactive Spring Integration users' life very much.

Context
I really suffer from understanding which channel adapter/ gateway has a reactive behavior or not, except in cases like ReactiveMongoDbStoringMessageHandler etc. I've also seen the need for this in https://github.com/spring-projects/spring-integration/issues/3771.

Start with the endpoint summary table in the linked Spring Integration documentation and review its inbound adapter, outbound adapter, inbound gateway, and outbound gateway entries. Compare examples such as ReactiveMongoDbStoringMessageHandler, then define a consistent signal for reactive support and clarify how async implementations should be treated. Done means the table clearly identifies the relevant capability for users.