Adding alternative SVG versions

[walkxcode]

Hi everyone,

Following my previous announcement, I’m looking to start including SVGs for both the primary and alternative versions of monochrome icons. So far, only the primary versions have been added.

There are many icons in the PNG folder with a -light or -alt version, but only the primary version is in the SVG folder.

If anyone is interested in helping out by creating PRs to add these, feel free to jump in!

Thanks in advance!
Bjorn