Social Icons Tray component

[thescientist13]

Summary

Coming out of #27 / #60 , it seems like it would make sense to make a shared "social tray" icon that can accept a fill color and forward that the actual SVG icons underneath. With a default value, it should make it easy to reuse this component and all its links / styles in one place, ideally.

Details

It would be nice to to have the fill color passed in a CSS variable, and I suppose the default fill color can be --color-secondary.

Using our styling guidelines, the social stray should only need to be a static Light DOM based component.

[thescientist13]

After the latest changes in #124 , we should use the header styles as the source of truth.