doc: add note about resource type in async_hooks

PR-URL: #41797
Reviewed-By: Stephen Belanger <admin@stephenbelanger.com>
Reviewed-By: Darshan Sen <raisinten@gmail.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Gerhard Stöbich <deb2001-github@yahoo.de>
Reviewed-By: Vladimir de Turckheim <vlad2t@hotmail.com>

doc/api/async_hooks.md

@@ -329,6 +329,8 @@ The `type` is a string identifying the type of resource that caused
 `init` to be called. Generally, it will correspond to the name of the
 resource's constructor.
 
+Valid values are:
+
 ```text
 FSEVENTWRAP, FSREQCALLBACK, GETADDRINFOREQWRAP, GETNAMEINFOREQWRAP, HTTPINCOMINGMESSAGE,
 HTTPCLIENTREQUEST, JSSTREAM, PIPECONNECTWRAP, PIPEWRAP, PROCESSWRAP, QUERYWRAP,
@@ -337,6 +339,9 @@ TTYWRAP, UDPSENDWRAP, UDPWRAP, WRITEWRAP, ZLIB, SSLCONNECTION, PBKDF2REQUEST,
 RANDOMBYTESREQUEST, TLSWRAP, Microtask, Timeout, Immediate, TickObject
 ```
 
+These values can change in any Node.js release. Furthermore users of [`AsyncResource`][]
+likely provide other values.
+
 There is also the `PROMISE` resource type, which is used to track `Promise`
 instances and asynchronous work scheduled by them.