tools: add 12.x to alternative docs versions

PR-URL: #27658 Reviewed-By: James M Snell <[email protected]> Reviewed-By: Rich Trott <[email protected]> Reviewed-By: Ruben Bridgewater <[email protected]> Reviewed-By: Colin Ihrig <[email protected]> Reviewed-By: Сковорода Никита Андреевич <[email protected]>

Author: richardlau

tools/doc/html.js

@@ -384,6 +384,7 @@ function altDocs(filename, docCreated){
 const[,docCreatedMajor,docCreatedMinor]=docCreated.map(Number);
 consthost='https://nodejs.org';
 constversions=[
+{num: '12.x'},
 {num: '11.x'},
 {num: '10.x',lts: true},
 {num: '9.x'},