Fix: types for setTimeout/setInterval calls

[mkslanc]

Issue #, if available:

When @types/node is installed (for example, in a parent folder), TypeScript may interpret calls to setInterval (and similar timers) as returning NodeJS.Timeout instead of number. This leads to inconsistent types across different environments and can cause issues in generated .d.ts files.

Description of changes:
To ensure a consistent approach that works regardless of whether Node types are present, we use ReturnType<typeof setInterval> (and similarly for setTimeout). This way, even if the compiler sees both the DOM and Node definitions, it will correctly infer a union type when necessary without unexpectedly locking us to NodeJS.Timeout alone. This approach also future‑proofs code by not relying on environment-specific declarations.

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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 87.05%. Comparing base (5acea6d) to head (a95240d).
Report is 3 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #5726   +/-   ##
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  Coverage   87.05%   87.05%           
=======================================
  Files         598      598           
  Lines       43703    43703           
  Branches     7163     7163           
=======================================
  Hits        38047    38047           
  Misses       5656     5656           

Flag	Coverage Δ
unittests	87.05% <ø> (ø)

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