Add `.no_drag_scroll()` to `OverflowBuilder`

[TheRedDeveloper]

Summary

Add .no_drag_scroll() to OverflowBuilder to disable mouse drag scrolling on scroll containers while keeping touch drag and scroll wheel scrolling.

Motivation

Drag scrolling on overflow containers is currently always enabled. On desktop, this can interfere with expected mouse interactions (selecting content, clicking elements during accidental micro-drags).

Proposed API

ui.element()
  .overflow(|o| o.scroll_y().no_drag_scroll())
  .children(|ui| {});

When .no_drag_scroll() is set:

• Mouse drag: does nothing (no drag scrolling)
• Touch drag: still scrolls
• Scroll wheel: still scrolls

Behavior

• Touch detection uses macroquad's touches() function. If touches() is non-empty during a press, it's touch input and drag scrolling still works.
• .no_drag_scroll() only affects mouse drag scrolling. Scroll wheel and touch-based scrolling are unaffected.