Ability to detect if touch input is available

## What problem does this solve or what need does it fill?

I would like my game to set up the UI a little differently if running on a device with a touchscreen. Enable some additional touch-only features, etc.

It would be very convenient if there was an API to detect if a touchscreen is present.

## What solution would you like?

Some sort of Resource that can be checked to indicate if the system the app is running on has a touchscreen / could provide touch input events.

Maybe also a predefined run condition for it.

## What alternative(s) have you considered?

Well, my current workaround is to have a "setting" in my game for whether touch-specific features are enabled. I can make it default to true for Android/iOS builds and false otherwise (but allowing the user to enable it in the game's settings).

Or I could assume a touchscreen is not available at first and have a system that can rebuild / setup the UI for touch as soon as it detects a Touch event at runtime.

It would still be much nicer if there was a way to detect the existence of a touch input ahead of time, though.