Add support for square sdk and add new features

[NikolaGavric94]

Added

• [x] Square SDK compatibility (ver. 16.0.0.20211117), removed old SquareConnect API
• [x] New scope field for identifying ORDER or LINE_ITEM discounts and taxes
• [x] New library inside require-dev for testing purposes: laravel/legacy-factories: '~1.1'

Changed

• [x] Internal workings of building different request objects sent to Square
• [x] Square classes root namespace and their correct paths
• [x] Internal way of handling exceptions/errors
• [x] All product discounts and taxes are now also inside order discounts and taxes with appropriate scope
• [x] Updated Readme.md
• [x] Updated DB schema graphics inside Wiki pages
• [x] Updated Wiki pages
• [x] Updated Changelog.md

Fixed

• [x] #60

[NikolaGavric94]

If anyone is able to help migrate the travis config to github actions I would appreciate it. There is some work done already by me, but by the looks of it, it seems something is missing because the pipeline is failing and the reason doesn't make sense

[NikolaGavric94]

Okay, github actions have been resolved, I will be finishing the documentation now and releasing a new version