Scratch-blocks: Touch event on PC should open on-screen keyboard

[cwillisf]

The convention on a Windows computer with a touch-screen is:

• A click event in a user-input field should not display an on-screen keyboard, but
• A touch event in a user-input field should display an on-screen keyboard.

We should probably follow this convention when choosing whether to display (for example) our number pad.

[tmickel]

@rachel-fenichel Btw I was curious if you tested this?

[rachel-fenichel]

Currently touch events on edge on windows are fairly broken--edge and IE don't implement the touch events API, only pointer events. I need to go back and test it again but I'm not optimistic right now.

[rachel-fenichel]

@chexbox Please keep your comments constructive.

[picklesrus]

This is working now on a surface tablet.