README is out of date [#3280969]

Problem/Motivation

The instruction when trying to download the MathJax library locally is out of date!

Steps to reproduce

1. Install and enable this module
$ composer require drupal/mathjax
(done)

2. Install the third-party MathJax software:
Download MathJax source from the MathJax website.
Un-archive it into your “libraries” directory.
You may need to create the “libraries” directory first.
Rename it to “MathJax”. When finished you should have this structure:
`/libraries/MathJax/MathJax.js`

Navigate to www.mathjax.org/#installnow , copy the link from the “Or simple download a copy of the latest distribution.”
( github.com/mathjax/MathJax/archive/master.zip )
cd web/libraries;
wget github.com/mathjax/MathJax/archive/master.zip ;
unzip master.zip ;
mv MathJax-master MathJax

There is no MathJax.js in that folder.. No MathJax.js in the Mathjax/es5 folder.

…/web/libraries/MathJax$ find | grep -i mathjax.js
(nothing)

Proposed resolution

Guessing that MathJax.org is distributing a TOO NEW of library. Either provide a link to an old enough version to download, unzip, rename or update the repository to make use of the current version from MathJax ?!