fix: UI issues

[LucasXu0]

• the cursor will be blocked if the background color of the text isn't transparent.

• expand the background color of the block component

[codecov]

Codecov Report

Attention: 6 lines in your changes are missing coverage. Please review.

Comparison is base (b5f8bd1) 80.20% compared to head (9202894) 80.27%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #530      +/-   ##
==========================================
+ Coverage   80.20%   80.27%   +0.06%     
==========================================
  Files         282      282              
  Lines       11999    12029      +30     
==========================================
+ Hits         9624     9656      +32     
+ Misses       2375     2373       -2     

Files	Coverage Δ
...component/selection/block_selection_container.dart	100.00% <100.00%> (ø)
...block_component/bulleted_list_block_component.dart	92.68% <100.00%> (ø)
...ading_block_component/heading_block_component.dart	92.10% <100.00%> (+0.10%)	⬆️
...block_component/numbered_list_block_component.dart	93.10% <100.00%> (+0.16%)	⬆️
...aph_block_component/paragraph_block_component.dart	98.59% <100.00%> (ø)
...t/quote_block_component/quote_block_component.dart	91.17% <100.00%> (+0.26%)	⬆️
...tor/block_component/standard_block_components.dart	100.00% <100.00%> (ø)
...ist_block_component/todo_list_block_component.dart	87.64% <100.00%> (+0.28%)	⬆️
...ib/src/editor/editor_component/service/editor.dart	100.00% <100.00%> (ø)
...component/service/ime/non_delta_input_service.dart	83.33% <100.00%> (ø)
... and 6 more

... and 1 file with indirect coverage changes

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