Update the codebase to the first release version (0.10.0)

[areee]

• Refactor the argument parser & add an enum for arg consts
• Refactor (move selected values print to an own method)
• Add 'run' command & refactor the main method
• Update pubspec.yaml (version & environment sdk)
• Add 'path' & 'yaml' dependencies + update the introduction in the main method
• Update readReceiptFile to use async-await
• Rename 'strings2Products' -> 'strings2ReceiptProducts'
• Update 'receiptProducts2CSV' (fix discount column generating condition)
• Fix a precision problem (1.605 -> 1.61)
• Fix another precision problem (0.975 -> 0.98)
• Update readme x 6
• Update readme (add version number & license badges)
• Update dart_kassakuitti_cli.dart (add a clue to the help command)