fix: block selection overflow

[LucasXu0]

closes #311

[LucasXu0]

#263 (comment)

And removed the limited number mentioned in the above link.

[codecov]

Codecov Report

Merging #312 (f14f31b) into main (87fd7ed) will increase coverage by 0.72%.
The diff coverage is 84.61%.

@@            Coverage Diff             @@
##             main     #312      +/-   ##
==========================================
+ Coverage   72.24%   72.96%   +0.72%     
==========================================
  Files         237      235       -2     
  Lines        9539     9454      -85     
==========================================
+ Hits         6891     6898       +7     
+ Misses       2648     2556      -92     

Impacted Files	Coverage Δ
.../block_component/rich_text/appflowy_rich_text.dart	87.86% <0.00%> (-1.03%)	⬇️
...nt/service/selection/mobile_selection_service.dart	0.00% <ø> (ø)
lib/src/render/selection/selectable.dart	50.00% <ø> (ø)
...block_component/numbered_list_block_component.dart	86.58% <37.50%> (-5.73%)	⬇️
...vider_block_component/divider_block_component.dart	62.90% <50.00%> (-2.68%)	⬇️
...t/image_block_component/image_block_component.dart	56.32% <60.00%> (-1.33%)	⬇️
...nent/base_component/widget/nested_list_widget.dart	100.00% <100.00%> (ø)
...block_component/bulleted_list_block_component.dart	92.40% <100.00%> (+0.40%)	⬆️
...ading_block_component/heading_block_component.dart	90.32% <100.00%> (-0.16%)	⬇️
...t/quote_block_component/quote_block_component.dart	89.65% <100.00%> (-0.18%)	⬇️
... and 6 more

... and 3 files with indirect coverage changes