feat: select multiple lines with block selection style

[LucasXu0]

Use the API below to select multiple lines with block selection style.

      final selection = Selection.collapsed(
        Position(path: path),
      );
      editorState.updateSelectionWithReason(
        selection,
        customSelectionType: SelectionType.block,
      );

      value.configuration = value.configuration.copyWith(
        padding: (_) => const EdgeInsets.symmetric(vertical: 8.0),
        blockSelectionAreaMargin: (_) => const EdgeInsets.symmetric(
          vertical: 1.0,
        ),
      );

[codecov]

Codecov Report

Attention: Patch coverage is 93.33333% with 1 line in your changes missing coverage. Please review.

Project coverage is 72.03%. Comparing base (8ae43d4) to head (95821be).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
lib/src/editor_state.dart	50.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #936      +/-   ##
==========================================
+ Coverage   72.02%   72.03%   +0.01%     
==========================================
  Files         318      318              
  Lines       15036    15046      +10     
==========================================
+ Hits        10829    10838       +9     
- Misses       4207     4208       +1     

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