tools: update alternative docs versions

Add `11.x` and mark `10.x` as `lts`.

PR-URL: https://github.com/nodejs/node/pull/23980
Reviewed-By: Refael Ackermann <refack@gmail.com>
Reviewed-By: Vse Mozhet Byt <vsemozhetbyt@gmail.com>
Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>

tools/doc/html.js

@@ -404,7 +404,8 @@ function altDocs(filename, docCreated) {
   const [, docCreatedMajor, docCreatedMinor] = docCreated.map(Number);
   const host = 'https://nodejs.org';
   const versions = [
-    { num: '10.x' },
+    { num: '11.x' },
+    { num: '10.x', lts: true },
     { num: '9.x' },
     { num: '8.x', lts: true },
     { num: '7.x' },