Update text selection when toggling checkbox

[amantoux]

When toggling a checkbox the cursor is set at the offset of the checkbox's line start

Fixes issues addressed by PR #400

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 88.24%. Comparing base (6abce16) to head (ad0f7c3).

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #441   +/-   ##
=======================================
  Coverage   88.24%   88.24%           
=======================================
  Files          62       62           
  Lines       10630    10637    +7     
=======================================
+ Hits         9380     9387    +7     
  Misses       1250     1250           

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[amantoux]

@Amir-P can you please review?
Essentially, this allows the check box to render it's own state while silently updating the document via the controller.
This avoids the re-build of the editor that would scroll to the cursor position while preserving the current text selection.