effects/mousemark: Add touchscreen and multi-touch drawing support in Mouse Marks effect

Disclaimer: This is my first attempt at contributing to open-source software, so please let me know if something could be done better. Thanks!

This merge request adds touchscreen drawing support into the Mouse Marks effect, allowing one or more freehand lines and arrows to be drawn simultaneously with a touch screen and mouse. The keybinds work as expected. Touchscreen support is enabled with a checkbox in the Mouse Marks config. Mouse-only drawing seems to be unaffected, and works as before. Tested on my laptop, works fine so far.

!5689 seems to do the same thing as this, but it looks incomplete, so making new MR.