Support Arc browser colors

[Jack5079]

Reference for CSS variables: https://arc.net/colors.html https://github.com/jbmagination/ArcDetectionPoC

A couple blockers:

• I don't know anyone in the Arc beta
• I don't know any Mac users
• Arc does not publish the default values of these colors so I don't know what each one means (for example when to use backgroundExtra vs backgroundSecondary, what is hover for)

[Jack5079]

• I don't know anyone in the Arc beta

https://arc.net/gift/mkbhd, time to find Mac users

[Jack5079]

Wait a minute that PoC has Little Arc colors as constants

[Jack5079]

Remembered I know someone with a Mac, here's the default theme (Light, idk if there's a default dark theme I didn't have enough time for that)

--arc-palette-foregroundPrimary: rgb(49, 57, 251);
--arc-palette-foregroundSecondary: rgb(132, 137, 251);
--arc-palette-foregroundTertiary: rgb(236, 237, 254);
--arc-palette-maxContrastColor: rgb(33, 42, 251);
--arc-palette-minContrastColor: rgb(236, 237, 254);
--arc-palette-backgroundExtra: rgba(253, 253, 255, 0.95);
--arc-palette-background: rgba(232, 233, 254, 0.957);
--arc-palette-focus: rgba(141, 146, 251, 0.976);
--arc-palette-hover: rgba(209, 211, 253, 0.96);
--arc-palette-cutoutColor: rgb(236, 237, 254);
--arc-palette-title: rgba(10, 13, 78, 0.965);
--arc-palette-subtitle: rgba(164, 167, 251, 0.97);
--arc-background-simple-color: rgba(0, 0, 0, 0);
--arc-background-gradient-color0: rgb(200, 202, 254);
--arc-background-gradient-color1: rgb(255, 230, 230);
--arc-background-gradient-color2: rgba(0, 0, 0, 0);
--arc-background-gradient-overlay-color0: rgba(0, 0, 0, 0);
--arc-background-gradient-overlay-color1: rgba(0, 0, 0, 0);
--arc-background-gradient-overlay-color2: rgba(0, 0, 0, 0);

[Jack5079]

https://twitter.com/quinn_mcginley/status/1603590567430086657 uses foregroundSecondary for the accent color, then what the hell is foregroundPrimary for?