doc: add branding to style guide

PR-URL: #23967
Reviewed-By: Richard Lau <riclau@uk.ibm.com>
Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com>
Reviewed-By: Matheus Marchini <mat@mmarchini.me>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Franziska Hinkelmann <franziska.hinkelmann@gmail.com>
Reviewed-By: Vse Mozhet Byt <vsemozhetbyt@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>

doc/STYLE_GUIDE.md

@@ -70,6 +70,8 @@
 * Use official styling for capitalization in products and projects.
   * OK: JavaScript, Google's V8
   * NOT OK: Javascript, Google's v8
+* Use _Node.js_ and not _Node_, _NodeJS_, or similar variants.
+  * When referring to the executable, _`node`_ is acceptable.
 
 See also API documentation structure overview in [doctools README][].