doc: readline write() is processed as input

Fixes: #4402
PR-URL: #8295
Reviewed-By: Anna Henningsen <[email protected]>
Reviewed-By: Colin Ihrig <[email protected]>

Author: jasnell

doc/api/readline.md

@@ -316,6 +316,9 @@ rl.on('line', (line) => {
 });
 ```
 
+*Note*: The `rl.write()` method will write the data to the `readline`
+Interface's `input` *as if it were provided by the user*.
+
 ## readline.clearLine(stream, dir)
 <!-- YAML
 added: v0.7.7