doc: add capitalization styling to STYLE_GUIDE

This is mostly an excuse to remind people that it's "V8" and not "v8"
when referring to the JavaScript engine.

PR-URL: #17163
Backport-PR-URL: #17765
Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: Vse Mozhet Byt <vsemozhetbyt@gmail.com>
Reviewed-By: Benjamin Gruenbaum <benjamingr@gmail.com>
Reviewed-By: Alexey Orlenko <eaglexrlnk@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Gireesh Punathil <gpunathi@in.ibm.com>

Author: Trott

doc/STYLE_GUIDE.md

@@ -69,6 +69,9 @@
 * Function returns should use the following format:
   * <code>* Returns: {type|type2} Optional description.</code>
   * E.g. <code>* Returns: {AsyncHook} A reference to `asyncHook`.</code>
+* Use official styling for capitalization in products and projects.
+  * OK: JavaScript, Google's V8
+  * NOT OK: Javascript, Google's v8
 
 [Em dashes]: https://en.wikipedia.org/wiki/Dash#Em_dash
 [Javascript type]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Grammar_and_types#Data_structures_and_types