chore(docs): added eslint to lint documentation code blocks (#2920)

* docs: added rule for code length

* chore: fixes based on vale errors

* changed to use eslint

* fixes using eslint

* added github action for documentation eslint

* changed allowed max-length

* fixed incorrect heading level

* removed comment

docs/content/add-plugins/mailchimp.md

@@ -59,15 +59,15 @@ Open `medusa-config.js` and add the new plugin into the `plugins` array:
 
 ```js title=medusa-config.js
 const plugins = [
-  ...,
+  // ...,
   {
     resolve: `medusa-plugin-mailchimp`,
     options: {
       api_key: process.env.MAILCHIMP_API_KEY,
-      newsletter_list_id: process.env.MAILCHIMP_NEWSLETTER_LIST_ID
-    }
-  }
-];
+      newsletter_list_id: process.env.MAILCHIMP_NEWSLETTER_LIST_ID,
+    },
+  },
+]
 ```
 
 ---
@@ -147,35 +147,37 @@ npm install axios
 Then, in the component you want to add the subscription form add the following code:
 
 ```jsx
-import axios from 'axios'
-import { useState } from "react";
+import axios from "axios"
+import { useState } from "react"
 
 export default function NewsletterForm() {
   const [email, setEmail] = useState("")
 
   function subscribe(e) {
-    e.preventDefault();
+    e.preventDefault()
     if (!email) {
-      return;
+      return
     }
 
-    axios.post('http://localhost:9000/mailchimp/subscribe', {
-      email
+    axios.post("http://localhost:9000/mailchimp/subscribe", {
+      email,
     })
       .then((e) => {
         alert("Subscribed sucessfully!")
         setEmail("")
       })
       .catch((e) => {
-        console.error(e);
-        alert("An error occurred");
+        console.error(e)
+        alert("An error occurred")
       })
   }
 
   return (
     <form onSubmit={subscribe}>
       <h2>Sign Up for our newsletter</h2>
-      <input type="email" name="email" id="email" placeholder="example@gmail.com"
+      <input 
+        type="email" name="email" id="email" 
+        placeholder="example@gmail.com"
         value={email} onChange={(e) => setEmail(e.target.value)} />
       <button type="submit">Subscribe</button>
     </form>