docs: add missing deprecated systemPreferences APIs to breaking-changes

docs/breaking-changes.md

@@ -368,6 +368,52 @@ in Electron 8.x, and cease to exist in Electron 9.x. The layout zoom level
 limits are now fixed at a minimum of 0.25 and a maximum of 5.0, as defined
 [here](https://chromium.googlesource.com/chromium/src/+/938b37a6d2886bf8335fc7db792f1eb46c65b2ae/third_party/blink/common/page/page_zoom.cc#11).
 
+### Deprecated events in `systemPreferences`
+
+The following `systemPreferences` events have been deprecated:
+* `inverted-color-scheme-changed`
+* `high-contrast-color-scheme-changed`
+
+Use the new `updated` event on the `nativeTheme` module instead.
+
+```js
+// Deprecated
+systemPreferences.on('inverted-color-scheme-changed', () => { /* ... */ })
+systemPreferences.on('high-contrast-color-scheme-changed', () => { /* ... */ })
+
+// Replace with
+nativeTheme.on('updated', () => { /* ... */ })
+```
+
+### Deprecated: methods in `systemPreferences`
+
+The following `systemPreferences` methods have been deprecated:
+* `systemPreferences.isDarkMode()`
+* `systemPreferences.isInvertedColorScheme()`
+* `systemPreferences.isHighContrastColorScheme()`
+
+Use the following `nativeTheme` properties instead:
+* `nativeTheme.shouldUseDarkColors`
+* `nativeTheme.shouldUseInvertedColorScheme`
+* `nativeTheme.shouldUseHighContrastColors`
+
+```js
+// Deprecated
+systemPreferences.isDarkMode()
+// Replace with
+nativeTheme.shouldUseDarkColors
+
+// Deprecated
+systemPreferences.isInvertedColorScheme()
+// Replace with
+nativeTheme.shouldUseInvertedColorScheme
+
+// Deprecated
+systemPreferences.isHighContrastColorScheme()
+// Replace with
+nativeTheme.shouldUseHighContrastColors
+```
+
 ## Planned Breaking API Changes (7.0)
 
 ### Deprecated: Atom.io Node Headers URL