doc: add a note on usage scope of AliasedBuffer

Explain usage context and scope of AliasedBuffer API and its
function in the C++ style guide. Provide an example code.

Fixes: https://github.com/nodejs/node/issues/22977

PR-URL: https://github.com/nodejs/node/pull/24724


Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Joyee Cheung <joyeec9h3@gmail.com>
Reviewed-By: Vse Mozhet Byt <vsemozhetbyt@gmail.com>