Update our MathJax solution to 3.x

[SteelWagstaff]

Latest version can be found here: https://github.com/mathjax/MathJax-src/releases (3.2 at time of last edit)

[ho-man-chan]

Update [created for issue pressbooks/private#1279]:
By updating Mathjax to 3.x or even 4.x, the following vulnerability would be fixed. This may be a breaking change and may require refactoring our implementation.

jsdom  <=16.5.3
Severity: moderate
Insufficient Granularity of Access Control in JSDom - https://github.com/advisories/GHSA-f4c9-cqv8-9v98
Depends on vulnerable versions of request
Depends on vulnerable versions of tough-cookie
No fix available
node_modules/mathjax-node/node_modules/jsdom
  mathjax-node  *
  Depends on vulnerable versions of jsdom
  node_modules/mathjax-node

request  *
Severity: moderate
Server-Side Request Forgery in Request - https://github.com/advisories/GHSA-p8p7-x288-28g6
Depends on vulnerable versions of tough-cookie
No fix available
node_modules/request
  request-promise-core  *
  Depends on vulnerable versions of request
  node_modules/request-promise-core
    request-promise-native  >=1.0.0
    Depends on vulnerable versions of request
    Depends on vulnerable versions of request-promise-core
    Depends on vulnerable versions of tough-cookie
    node_modules/request-promise-native

tough-cookie  <4.1.3
Severity: moderate
tough-cookie Prototype Pollution vulnerability - https://github.com/advisories/GHSA-72xf-g2v4-qvf3
No fix available
node_modules/mathjax-node/node_modules/tough-cookie
node_modules/request-promise-native/node_modules/tough-cookie
node_modules/request/node_modules/tough-cookie