Add: Marks

Edit: Code refactoring and added result and history label minimum font size in Storyboard

Edit: updates .gitignore

Edit: updates .gitignore

Edit: Operation enum and Updates private functions as private extensions

Test fork

Add: activated percentage and plus/minus buttons

Add: historyLabel

Add: Decimal values are now displayed correctly.

Add: added Number, operation, equals, clear button and starts logic

Add: Result Text Field

Add: Storyboard Button and added button Storyboard

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Add: .gitignore

Update UserInterfaceState.xcuserstate