New "Mozilla" brand assets

[janbrasna]

The following contain "m" or "://" design and need updating with 2024 branding:

Logos:

• logos/mozilla/logo-word-hor-white.svg
• logos/mozilla/logo-word-hor.svg
• logos/mozilla/logo-flat-white.svg
• logos/mozilla/logo-flat.svg
• logos/mozilla/logo.svg

Icons:

• icons/mozilla.svg
• icons/social/mozilla/black.svg
• icons/social/mozilla/white.svg

Most likely an assortment of wormark, logo lockup, and symbol instances.

[stephaniehobson]

Fixed in #101