Add Firefox Relay logos (fixes #79)

[maureenlholland]

We need to add Firefox Relay logos to Protocol, so we can easily use them in wordmarks and logos on Bedrock. I've added flat versions, but I'm not sure these are needed. No og.png version yet. All svg files have been optimized with SVGO.

The following logos should be available in regular and dark-theme (-white) variations: (See Firefox Monitor for example of full logo set)

• [ ] Logo
• [ ] Logo Flat (monochrome)
• [ ] Wordmark Horizontal
• [ ] Wordmark Horizontal Stacked
• [ ] Wordmark Vertical
• [ ] Wordmark Vertical Stacked

Changelog is updated

You can view a local demo with this Protocol branch http://localhost:3000/demos/logo.html

[maureenlholland]

todo:

• vertical wordmarks
• stacked wordmarks (horizontal and vertical)
• flat logos
• fix optimization errors

[maureenlholland]

Looks like we might need to reduce the size of the text a smidge, based on comparison to other Firefox products:

[maureenlholland]

ℹ️ on hold till we get a definitive font size

update: 1/11/21 - Elise confirmed the Relay font was too big and updated the Figma master component to match existing Firefox wordmark font

[maureenlholland]

@reemhamz @craigcook I think this is ready for review!