Make SVG honor the scale configuration option. (mathjax/MathJax#2376)

[dpvc]

This PR fixes the problem where SVG output doesn't take the scale configuration option into account.

Resolves issue mathjax/MathJax#2376.

[working-name]

I can confirm SVG renderer honors scale configuration changes across the following browsers:

Safari 12.1 / 13.0.5
iOS 13.3.1 Safari (no idea what version that is)
Chrome 80.0.3987.132/149
Firefox 74.0
Epic 75.0.3770.100 (older chromium based)
Waterfox Current 2020.03
Firefox Quantum 60.6.1esr
Firefox Quantum 68.6.0esr
Edge 25.10586.0.0 (EdgeHTML 13.10586)
Internet Explorer 11.162.10586.0 (js patch made it spit a JS error 
but issue2376 branch compiled version works just fine)

[dpvc]

@working-name, Great! Thanks for the thorough testing.

js patch made it spit a JS error but issue2376 branch compiled version works just fine

You probably need

        ready: function () {

rather than

        ready() {

in IE11.

Again, thanks for the support!

[working-name]

You are absolutely right. IE is now happy with the patch too, and honors scaling.

[dpvc]

Thanks for the confirmation!

[zorkow]

lgtm.