doc: recommend not using libuv node-api function

- update documentation recommend not using the
  napi_get_uv_event_loop  function. It should not be
  need for most if not all uses cases now that the
  API is more complete.

Signed-off-by: Michael Dawson <midawson@redhat.com>
PR-URL: nodejs#53521
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Chengzhong Wu <legendecas@gmail.com>
Reviewed-By: Gabriel Schulhof <gabrielschulhof@gmail.com>
Reviewed-By: Marco Ippolito <marcoippolito54@gmail.com>

doc/api/n-api.md

@@ -6241,6 +6241,12 @@ NAPI_EXTERN napi_status napi_get_uv_event_loop(node_api_nogc_env env,
 * `[in] env`: The environment that the API is invoked under.
 * `[out] loop`: The current libuv loop instance.
 
+Note: While libuv has been relatively stable over time, it does
+not provide an ABI stability guarantee. Use of this function should be avoided.
+Its use may result in an addon that does not work across Node.js versions.
+[asynchronous-thread-safe-function-calls](https://nodejs.org/docs/latest/api/n-api.html#asynchronous-thread-safe-function-calls)
+are an alternative for many use cases.
+
 ## Asynchronous thread-safe function calls
 
 JavaScript functions can normally only be called from a native addon's main