Random case/spongetext case converter implementation

[ahrGNUts]

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
• Other (please describe):

What is the current behavior?

Implemented the case converter described in the issue below:
Issue Number: #1055

What is the new behavior?

• New converter button 'raNdoM cASe' added to Text Analyzer and Utilities
• Text character cases are randomly changed in the string when the button is clicked

Other information

Quality check

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

Hi,
Thank you for this contribution. It looks all good to me :)