Add trackScrollEvents setting to docs (appium#12791)

* Add trackScrollEvents setting to docs

* Add more info on scroll tracking

* Typo patrol

docs/en/advanced-concepts/settings.md

@@ -65,6 +65,7 @@ Note that the actual commands you would use in your test script differ based on
 |`waitForSelectorTimeout`| Int (milliseconds) which is the same as [setWaitForSelectorTimeout](https://developer.android.com/reference/android/support/test/uiautomator/Configurator.html#setWaitForSelectorTimeout(long)). If a negative value is given, it would set to default(10 * 1000 milliseconds). Handled by [UiAutomator Configurator](https://developer.android.com/reference/android/support/test/uiautomator/Configurator.html) in Android API 18 and above. | e.g., `10000` |
 |`normalizeTagNames`| Translate all class names used as XML tags to the limited set of ASCII characters supported by Apache Harmony library. Used by default in Android to avoid possible XML parsing exceptions caused by XPath lookup. The translation is based on [junidecode](https://github.com/gcardone/junidecode). This prevents [this error case](https://github.com/appium/appium/issues/11854). Defaults to `false`. | `false` or `true` |
 |`shutdownOnPowerDisconnect`| Shutdown the server through the broadcast receiver on [ACTION_POWER_DISCONNECTED](https://developer.android.com/reference/android/content/Intent.html#ACTION_POWER_DISCONNECTED). Defaults to `true` | `false` or `true` |
+|`trackScrollEvents`| Turn on or off the tracking of scroll events as they happen. If `true`, a field, `lastScrollData`, is added to the results of `getSession`, which can then be used to check on scroll progress. Turning this feature off significantly increases touch action performance. Defaults to `true` | `true` or `false` |
 
 ### iOS Only