events: deprecate event.srcElement

`event.srcElement` is deprecated. We can use `event.target`
instead.

Refs: https://developer.mozilla.org/en-US/docs/Web/API/Event/srcElement

doc/api/deprecations.md

@@ -3334,6 +3334,19 @@ In a future version of Node.js, [`message.headers`][],
 [`message.headersDistinct`][], [`message.trailers`][], and
 [`message.trailersDistinct`][] will be read-only.
 
+### DEPXXXX: `event.srcElement`
+
+<!-- YAML
+changes:
+  - version: REPLACEME
+    pr-url: https://github.com/nodejs/node/pull/46085
+    description: Documentation-only deprecation.
+-->
+
+Type: Documentation-only
+
+The [`event.srcElement`][] is deprecated. Use [`event.target`][] instead.
+
 [NIST SP 800-38D]: https://nvlpubs.nist.gov/nistpubs/Legacy/SP/nistspecialpublication800-38d.pdf
 [RFC 6066]: https://tools.ietf.org/html/rfc6066#section-3
 [RFC 8247 Section 2.4]: https://www.rfc-editor.org/rfc/rfc8247#section-2.4
@@ -3384,6 +3397,8 @@ In a future version of Node.js, [`message.headers`][],
 [`domain`]: domain.md
 [`ecdh.setPublicKey()`]: crypto.md#ecdhsetpublickeypublickey-encoding
 [`emitter.listenerCount(eventName)`]: events.md#emitterlistenercounteventname
+[`event.srcElement`]: events.md#eventsrcelement
+[`event.target`]: events.md#eventtarget
 [`events.listenerCount(emitter, eventName)`]: events.md#eventslistenercountemitter-eventname
 [`fs.FileHandle`]: fs.md#class-filehandle
 [`fs.access()`]: fs.md#fsaccesspath-mode-callback

doc/api/events.md

@@ -1850,8 +1850,11 @@ This is not used in Node.js and is provided purely for completeness.
 
 <!-- YAML
 added: v14.5.0
+deprecated: REPLACEME
 -->
 
+> Stability: 0 - Deprecated
+
 * Type: {EventTarget} The `EventTarget` dispatching the event.
 
 Alias for `event.target`.