Add triple-tap gesture to select paragraph

[TSchattschneider]

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Use case

Triple-tap to select paragraph is missing from QuillEditor, despite being standard behavior in iOS/macOS text fields, Google Docs, Word, and most modern text editors. Currently users must long-press and drag to select a full paragraph.

Proposal

Implement triple-tap gesture detection to select the entire paragraph (Quill document node), following the existing gesture pattern architecture.

Implementation Details

Changes:

• Extends consecutive tap detection: _doubleTapTimer → _consecutiveTapTimer with tap count tracking
• Adds selectParagraph() and selectParagraphAtPosition() methods to RenderEditor
• 3 files changed: +112 lines, -25 lines

Edge cases handled:

• Excludes trailing newlines from selection

Consistent with other selection behavior:

• Tapping past end of text produces collapsed cursor
• Respects Quill node boundaries
• Shows toolbar automatically after selection

I have a working implementation ready: https://github.com/elea-ai/flutter-quill/tree/feature/triple-tap-to-select-paragraph

Rationale

• Standard UX pattern
• Backwards compatible - Only adds new gesture, doesn't change existing single/double-tap behavior
• Follows existing patterns - Mirrors selectWord() implementation and gesture detection architecture

Do you require any other adjustments to meet project standards?