Updated builds of API v1.2 and v1.3 released with fixes for iOS 13

[Jason Merrill]

The recent release of iOS 13 and iPadOS required some small but important updates to the Desmos calculator API. Specifically:

* On touch devices, the graphing calculator defaults to showing an onscreen keypad, but on non-touch devices, the onscreen keypad defaults to being minimized. The method we use to detect touch devices needed to be updated for iOS 13 in order to make sure that the onscreen keypad is shown by default on iPads.
* Some changes were required to maintain easy screen reader navigation between calculator expressions in VoiceOver.

We have back-ported these changes to the last two stable releases of the API (v1.2 and v1.3).

For partners who self-host the API

We have pushed new builds of API v1.2 and v1.3 to your shared repository. We recommend updating to a new build to maintain the best user experience on iOS 13.

For partners who load the API from desmos.com

No action is necessary. These changes have already been applied to API v1.2 and v1.3 on desmos.com, and your users will automatically get updated versions.