Consider adding "Libre Franklin" to the font family

[sandbergja]

Background

• The Communications office brand guide and core assets says "Libre Franklin is the central typeface within the new typographic system"
• Lux currently uses franklin-gothic-urw, rather than Libre Franklin

Acceptance criteria

• Libre Franklin is added to the Lux font family design tokens. For backwards compatibility, we could keep franklin-gothic-urw in the font family as well.

[sdellis]

@sandbergja
I think that we should remove franklin-gothic-urw if Libre Franklin is what we should be using. People can pin to previous release versions for backwards compatibility. Fonts can add a lot of weight to the dist package, so we should minimize their inclusion.