Add support for touchscreen devices.

[xyaman]

This commit adds support for touchscreen devices by ignoring the "Show Popup" keybind if "Show popup on hover" is enabled in the settings.

The "mousedown" listener event had issues on touchscreen devices because tapping or hovering over a word would also trigger a click event. To address this, a "Touchscreen Support" option has been added to the settings, which changes the behavior to only hide the popup on the "onmouseleave" event.

Currently, on small screens, the popup sometimes does not fully appear on the screen.

[xyaman]

I found a bug in the current implementation, where clicking on a word while the popup is displayed may cause it to hide and fail to show the new word's information. This is because sometimes "onmouseleave" event is triggered after the "onmouseenter" event. (This only happens if touchscreen support is enabled)

[xyaman]

Current bug: If the screen is small, the popup may readjust its position (e9d6557da55694634e3f4c8f1a383b1977434932) and sometimes the mine/review buttons can be pressed accidentally because the touch position could overlap with the button position.

Some ideas I've thought of are:

• Make the popup adjust its size automatically to avoid repositioning and the resulting bug.
• If the popup needs to be repositioned, add a small offset to prevent accidental clicking."

Edit: It seems this only happens when fade animation is disabled