fix: apply padding to right side multi-line markers

[akoreman]

Issue #, if available: NA

Description of changes: Currently, we apply a padding of 4px to the left side of multi line markers but no padding to the right side, making it hard to style both edges the same way. This adds a 4px padding to the right side of multi line selections.

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Pull Request Checklist:

• No backwards incompatible changes were made to Ace's public interface which is defined through the main typings file (ace.d.ts) and its references:
  • https://github.com/ajaxorg/ace/blob/master/ace.d.ts
  • https://github.com/ajaxorg/ace/blob/master/ace-modes.d.ts
  • https://github.com/ajaxorg/ace/blob/master/ace-extensions.d.ts

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 86.97%. Comparing base (a6ead2f) to head (2b7a830).
Report is 1 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #5636   +/-   ##
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  Coverage   86.97%   86.97%           
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  Files         594      594           
  Lines       43395    43395           
  Branches     7170     7170           
=======================================
  Hits        37742    37742           
  Misses       5653     5653           

Flag	Coverage Δ
unittests	86.97% <100.00%> (ø)

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