Fix: recursive readdirSync for NodeJS < 20.1.0

[mkslanc]

Issue #, if available:

Description of changes:
Read all files with all subdirectories due to manual recursion

By submitting this pull request, I confirm that you can use, modify, copy, and redistribute this contribution, under the terms of your choice.

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

[github-actions]

One of the public type files has been updated, plase make sure there are no backwards incompatible changes done in the PR.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 86.97%. Comparing base (560f5d3) to head (4df1595).
Report is 2 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #5645   +/-   ##
=======================================
  Coverage   86.97%   86.97%           
=======================================
  Files         594      594           
  Lines       43395    43395           
  Branches     7170     7170           
=======================================
  Hits        37742    37742           
  Misses       5653     5653           

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

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.