Feat: Extension to show whitespaces in selection

[mkslanc]

Issue #, if available:

Description of changes:
This PR introduces a new extension that highlights whitespaces within selected text regions, making invisible characters visible for better code editing experience.

• Visualizes spaces and tabs within selected text
• Automatically removes markers when selection changes or extension is disabled
• Includes styling for both light and dark themes
• Integrates with existing text marker system

screen-capture.-.2025-07-15T182714.007.webm

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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