[Feature Request] Add Square as a Payment Gateway

We really need to have Square ( aka "Squareup" as a Payment Gateway in Invoice Ninja.

I will find and hire interested devs to bid and begin work.
Only 1 active worker will be selected to work at a time.

![2021-04-15_21-20-30](

I don't know weather this needs to be done via API or not, but I can provide a Square business account for testing
![2021-04-15_21-43-09](

![2021-04-15_21-54-35](


Reference



Requirements
1) Need Gateway added
2) Gateway needs to function properly
3) Payment needs to be Updated and Recorded properly in Invoice Ninja