Bug 1878950: Add link to FF HCM pref r=nlapre

Differential Revision: https://phabricator.services.mozilla.com/D200872

Author: MReschenberg

accessible/docs/HCMMediaQueries.md

@@ -9,8 +9,8 @@ The `forced-colors` media query has two values: `active` and `none`. The resolve
 * The `none` state indicates documents can use any colors to render content.
 * The `active` state indicates a user has OS or browser settings that limit the color palette available to the User Agent.
 
-In Firefox's default configuration, the `active` state is triggered when a user has Windows High Contrast Mode enabled, Linux High Contrast Themes, or [Firefox High Contrast Mode](https://firefox-source-docs.mozilla.org/accessible/ColorsAndHighContrastMode.html#the-colors-dialog) (FF HCM) enabled. All of these forced-colors modes offer users a limited amount of color customisation. In Windows, users can override seven colors, and with Firefox High Contrast Mode users can override four. On Linux, the entire system theme is overridden. MacOS's "Increase Contrast" setting does **not** trigger `forced-colors: active` because it does not limit the color palette available to UA's.
-> **NOTE:** MacOS's "Increase Contrast" setting **will** trigger `forced-colors: active` (in non-chrome web content) if it is enabled in combination with FF HCM's "Only with High Contrast Themes" option. Because FF HCM defaults to "Never" on macOS, enabling  "Increase Contrast" alone will not trigger `forced-colors: active`. Similarly, if a user disables FF HCM while Win HCM or Linux HCT are enabled, `forced-colors` (in content) will evaluate to `none`.
+In Firefox's default configuration, the `active` state is triggered when a user has enabled Windows High Contrast Mode or [Firefox High Contrast Mode](https://firefox-source-docs.mozilla.org/accessible/ColorsAndHighContrastMode.html#the-colors-dialog) (FF HCM). Both of these forced-colors modes offer users a limited amount of color customisation. In Windows, users can override seven colors, and with Firefox High Contrast Mode users can override four. MacOS's "Increase Contrast" setting does **not** trigger `forced-colors: active` because it does not limit the color palette available to UA's.
+> **NOTE:** MacOS's "Increase Contrast" setting **will** trigger `forced-colors: active` (in non-chrome web content) if it is enabled in combination with FF HCM's "Only with High Contrast Themes" option. This is also true on Linux. Because [FF HCM defaults to "Never" on non-Windows platforms](https://searchfox.org/mozilla-central/rev/896042a1a71066254ceb5291f016ca3dbca21cb7/modules/libpref/init/StaticPrefList.yaml#1195-1199), enabling  "Increase Contrast" or Linux High Contrast Themes alone will not trigger `forced-colors: active`. Similarly, if a user disables FF HCM while Win HCM is enabled, `forced-colors` (in content) will evaluate to `none`.
 
 #### CSS System Colors