clicking back button once to close the app if it's opened through notifications

as the title says, add an option to make the app close and instantly go back to using the previews app when you open it through notifications when clicking the back button. and yes i'm aware it already does that but not when using back button to open the channel drawer which is also a really cool feature that everyone got used to and hard to sacrifice. this would be really helpful for users who can't reply directly from notifications (on android 7 and older) and others (like me) who simply don't use it at all.