fix: add prompt to save changes when closing an edited file

[Nithishvb]

Description

Related Issues

Closes: #2070

Type of Change

• [x] Bug fix
• [ ] New feature
• [ ] Documentation update
• [ ] Release
• [ ] Refactor
• [ ] Other (please describe):

Testing

Screenshots (if applicable)

Additional Notes

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[!IMPORTANT] Adds prompt to save or discard changes when closing an edited file, with state management and function updates in index.tsx and IDEManager.

• Behavior:
  • Adds prompt to save or discard changes when closing an edited file in index.tsx.
  • Handles unsaved changes when closing all files.
• State Management:
  • Introduces showUnsavedDialog and pendingCloseAll state variables in index.tsx.
• Functions:
  • Adds discardChanges() in index.tsx to discard unsaved changes.
  • Updates closeFile() and closeAllFiles() in index.tsx to handle unsaved changes.
  • Adds discardFileChanges() in IDEManager in index.ts to reset file content and dirty state.

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