Add Node 12 to the first list of versions

PR-URL: #27414
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: Roman Reiss <me@silverwind.io>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Yongsheng Zhang <zyszys98@gmail.com>

CHANGELOG.md

@@ -2,7 +2,8 @@
 
 Select a Node.js version below to view the changelog history:
 
-* [Node.js 11](doc/changelogs/CHANGELOG_V11.md) - **Current**
+* [Node.js 12](doc/changelogs/CHANGELOG_V12.md) - **Current**
+* [Node.js 11](doc/changelogs/CHANGELOG_V11.md) - Current
 * [Node.js 10](doc/changelogs/CHANGELOG_V10.md) — **Long Term Support**
 * [Node.js 9](doc/changelogs/CHANGELOG_V9.md) — End-of-Life
 * [Node.js 8](doc/changelogs/CHANGELOG_V8.md) — Long Term Support