doc: use sentence case in readme introduction

PR-URL: #41874
Refs: https://docs.microsoft.com/en-us/style-guide/a-z-word-list-term-collections/w/web-world-wide-web-www
Reviewed-By: Antoine du Hamel <duhamelantoine1995@gmail.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Tobias Nießen <tniessen@tnie.de>

Author: Mesteery

README.md

@@ -12,7 +12,7 @@
 
 Node.js is an open-source, cross-platform, JavaScript runtime environment.
 
-For information on using Node.js, see the [Node.js Website][].
+For information on using Node.js, see the [Node.js website][].
 
 The Node.js project uses an [open governance model](./GOVERNANCE.md). The
 [OpenJS Foundation][] provides support for the project.
@@ -763,7 +763,7 @@ license text.
 
 [Code of Conduct]: https://github.com/nodejs/admin/blob/HEAD/CODE_OF_CONDUCT.md
 [Contributing to the project]: CONTRIBUTING.md
-[Node.js Website]: https://nodejs.org/
+[Node.js website]: https://nodejs.org/
 [OpenJS Foundation]: https://openjsf.org/
 [Strategic initiatives]: doc/contributing/strategic-initiatives.md
 [Technical values and prioritization]: doc/contributing/technical-values.md