Fix missing assets

[bertdeblock]

Restores the public assets that were removed in #211.
Unsure if this is the right fix, but exactly these assets are still used in the index.html file:

• https:/voltidev/ember-svg-jar/blob/master/packages/ember-svg-jar/public/index.html#L107
• https:/voltidev/ember-svg-jar/blob/master/packages/ember-svg-jar/public/index.html#L204
• https:/voltidev/ember-svg-jar/blob/master/packages/ember-svg-jar/public/index.html#L205

Closes #233.

[bertdeblock]

@jherdman Would you mind giving this a review? The icon viewer is broken in v2.4.0 in both classic and Embroider builds.

[jherdman]

Many thanks for the fix! I'll put together a release right now.

[bertdeblock]

Thanks for the release @jherdman!

[tdwesten]

yeah @jherdman thanks!