Added check for update for extensions

[veler]

Pull request type

Please check the type of change your PR introduces:

• Bugfix
• New feature or enhancement
• UI change (please include screenshot!)
• Code style update (formatting, renaming)
• Refactoring (no functional changes, no api changes)
• Build related changes
• Documentation content changes
• Internationalization and localization
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What is the current behavior?

Issue Number: N/A

What is the new behavior?

When Check for update on start option is ON, DevToys will check for update of extension and notify the user about it in the UI. It won't install the update automatically (maybe something to add in the future)

Other information

Quality check

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• Did you follow the code style guideline as described in CONTRIBUTING.md
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