Add a dynamic shortcut for "Assist" to make it easier to bind to hotkeys (power button long-press) on Samsung Phones

**Is your feature request related to a problem? Please describe.**
There seems to be no specific "Assist"- app-action.

**Describe the solution you'd like**
Add a specific "Assist" app-action

**Additional context**
On Samsung Phones you can link a hold of the power-button to bixby. Via a plugin (Good Lock -> Routines +) it's possible to create a "bixby routine" (automation), where holding the power button launches an app or an app-action.
Home Assistant doesn't seem to expose a specific Assist app action (or any app action, which you might also get when tap-and-holding the app icon).

This would make Assist way easier to access for daily use, without the need to unlock the phone first.