Add enums to sort by browser feature support

[jcscottiii]

No description provided.

[jcscottiii]

@jrobbins I currently use desktop_availability_{browser}_{direction} to match the column keys in the frontend:

webstatus.dev/frontend/src/static/js/components/webstatus-overview-cells.ts

Lines 61 to 64 in b9e031f

	DesktopAvailabilityChrome = 'desktop_availability_chrome',
	DesktopAvailabilityEdge = 'desktop_availability_edge',
	DesktopAvailabilityFirefox = 'desktop_availability_firefox',
	DesktopAvailabilitySafari = 'desktop_availability_safari',

But when we bring on mobile support (#996), we will use the keys from web features: https://github.com/web-platform-dx/web-features/blob/580ce2ca36a2a603efa15df46592569a08f802d0/packages/compute-baseline/src/baseline/core-browser-set.ts#L3-L12

export const identifiers = [
  "chrome",
  "chrome_android",
  "edge",
  "firefox",
  "firefox_android",
  "safari",
  "safari_ios",
];

Thoughts on removing the desktop_ prefix so that enum will be availability_{browser}_{direction}?

[jrobbins]

Thoughts on removing the desktop_ prefix so that enum will be availability_{browser}_{direction}?

That seems fine. It is shorter, and for the mobile cases, the browser name includes the word to differentiate from desktop.