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/add-plugins/sendgrid.mdx

@@ -22,7 +22,7 @@ By integrating SendGrid with Medusa, you’ll be sending email notifications to
 
 ## Prerequisites
 
-Before going further with this guide make sure you have a Medusa server set up. You can follow our [Quickstart guide](../quickstart/quick-start.md).
+Before going further with this guide make sure you have a Medusa server set up. You can follow the [Quickstart guide](../quickstart/quick-start.md).
 
 You also must have [Redis configured on your Medusa server](/tutorial/set-up-your-development-environment#redis). Sending emails is done through Subscribers, which uses Redis as the event queue. If you don’t set up Redis, the plugin will not send emails.
 
@@ -42,7 +42,7 @@ If you choose to give the API Key restricted access, make sure to at least give
 
 :::
 
-Once you create the API key, the key will be shown for one time only. So, make sure to copy and save it somewhere for later usage.
+Once you create the API key, the key will be shown for one time only. Make sure to copy and save it somewhere for later usage.
 
 ### Email Templates
 
@@ -3953,7 +3953,7 @@ To test it out, perform an action that would trigger one of the emails being sen
 
 :::tip
 
-If you don’t have a storefront installed, check out our [Gatsby](../starters/gatsby-medusa-starter.md) or [Next.js](../starters/nextjs-medusa-starter.md) starters to create a storefront in minutes.
+If you don’t have a storefront installed, check out the [Gatsby](../starters/gatsby-medusa-starter.md) or [Next.js](../starters/nextjs-medusa-starter.md) starters to create a storefront in minutes.
 
 :::