Speed up requiring index.js file

[bertdeblock]

Ember CLI requires every addon's index.js file when running any command.
I noticed that requiring ember-svg-jar's index.js file takes a bit of time.
This PR should speed things up a bit by only requiring some packages when they are actually used.

Before: 170-180ms
After: 25-30ms

Tested on an Apple M1 Pro MacBook using:

console.time('require');
require('./index.js');
console.timeEnd('require');

[evoactivity]

I like the look of this, quite a significant speed improvement.

I've been given write access and npm access today but I've just released 2.4.3 so not going to merge this right away but it's on my radar to merge in with next release.

[bertdeblock]

Thanks @evoactivity!

[evoactivity]

This has been merged and released into 2.4.4