docs: integrate Vale for documentation linting (#2242)

* added value rules

* resolved errors raised by vale

* added github action

* fixes to github action

* added details in contribution guidelines

* added rule for numbers

* limited checks to errors

docs/content/advanced/backend/payment/overview.md

@@ -20,7 +20,7 @@ A Payment Provider in Medusa is a method to handle payments in selected regions.
 
 Payment Providers can be integrated with third-party services that handle payment operations such as capturing a payment. An example of a Payment Provider is Stripe.
 
-Payment Providers can also be related to a custom way of handling payment operations. An example of that is cash on delivery (COD) payment methods or Medusa’s [manual payment provider plugin](https://github.com/medusajs/medusa/tree/master/packages/medusa-payment-manual) which provides a minimal implementation of a payment provider and allows store operators to manually handle order payments.
+Payment Providers can also be related to a custom way of handling payment operations. An example of that is Cash on Delivery (COD) payment methods or Medusa’s [manual payment provider plugin](https://github.com/medusajs/medusa/tree/master/packages/medusa-payment-manual) which provides a minimal implementation of a payment provider and allows store operators to manually handle order payments.
 
 ### How Payment Provider is Created