DEVDOCS-5373: update Add Square v2 (#8)

<!-- Ticket number or summary of work -->
# [DEVDOCS-5373]


## What changed?
Add Square v2

## Release notes draft

Draft
The newly-released Square V2 payment gateway is available for stored
instrument data. See the list of [compatible payment gateways].

Examples:
* The newly-released [X feature] is now available to use. Now, you’ll be
able to [perform Y action].
* We're happy to announce [X feature], which can help you [perform Y
action].
* [X feature] helps you to create [Y response] using the [Z query
parameter]. Now, you can deliver [ex, localized shopping experiences for
your customers].
* Fixed a bug in the [X endpoint]. Now the [Y field] will appear when
you click [Z option]. -->
* 

## Anything else?
Old PR: bigcommerce/dev-docs#2085

ping {names}


[DEVDOCS-5373]:
https://bigcommercecloud.atlassian.net/browse/DEVDOCS-5373?atlOrigin=eyJpIjoiNWRkNTljNzYxNjVmNDY3MDlhMDU5Y2ZhYzA5YTRkZjUiLCJwIjoiZ2l0aHViLWNvbS1KU1cifQ

---------

Co-authored-by: Sarah Riehl <[email protected]>

docs/api-docs/payments/payments-api-overview.mdx

@@ -76,6 +76,7 @@ The following table lists the payment gateways that are compatible with our publ
 | QuickBooks Payments                      |     | ✓ |
 | Sage Pay/Protx VSP Direct                |     | ✓ |
 | SecureNet        |                             | ✓ |
+| Square v2        | ✓                     |         |
 | Stripe           | ✓                     | ✓ |
 | StripeV3         | ✓                     | ✓ |
 | StripeV4         | ✓                     | ✓ |