Scrolling on mobile opens edit widget at random

Describe the current behavior

The UI treats two tap scrolls in quick succession as a double-tap, even if they're on different cells or UI elements.

Steps to reproduce

1. Open a multi-column Grist on mobile
2. Try to scroll around at anything other than a snail's pace
3. The edit cell widget appears for the active cell. This might seem to be at random, frustrating users.

Describe the expected behavior

Double-tap should only apply if on the same UI element and within a reasonable distance, or as long as it didn't trigger an actual scroll.

Where have you encountered this bug?

• On docs.getgrist.com
• On a self-hosted instance

Instance information (when self-hosting only)

• Grist instance:
  • Version: 1.7.17
  • Installation mode: docker

Confirmed on latest Chrome on Android, Chrome Desktop, and Firefox Desktop.