Add support for the predictive back gesture

[candrews]

Checklist

• [X] I have used the search function to see if someone else has already submitted the same feature request.
• [X] I will describe the problem with as much detail as possible.
• [X] This issue only contains a request for one single feature, not multiple (related) features.

App version

6.312

Problem you are trying to solve

Android 13 (API level 33) introduces a predictive back gesture for Android devices such as phones, large screens, and foldables.

Suggested solution

I believe K-9 Mail uses default back navigation, so enabling this functionality should be as simple as opting in by updating AndroidManifest.xml, in the <application> tag, set the android:enableOnBackInvokedCallback flag to true.

See https://developer.android.com/guide/navigation/predictive-back-gesture#opt-predictive

Screenshots / Drawings / Technical details

Here's how predictive back looks: