docs: fixed keywords usage in some pages (#14140)

* docs: fixed keywords usage in some pages

* fix vale error

* fix vale error

www/apps/cloud/app/emails/page.mdx

@@ -16,6 +16,16 @@ import { ChevronUpDown } from "@medusajs/icons"
 
 export const metadata = {
   title: `Medusa Emails`,
+  keywords: [
+    "email",
+    "mail",
+    "medusa mail",
+    "transactional email",
+    "marketing email",
+    "email service",
+    "cloud email",
+    "medusa emails",
+  ],
 }
 
 # {metadata.title}

www/apps/cloud/app/sign-up/page.mdx

@@ -1,3 +1,11 @@
+---
+keywords:
+  - deploy
+  - deployment
+  - production
+  - cloud
+---
+
 export const metadata = {
   title: `Sign Up for Cloud`,
   keywords: ["deploy", "deployment", "production", "cloud"],

www/apps/resources/app/how-to-tutorials/tutorials/saved-payment-methods/page.mdx

@@ -20,6 +20,13 @@ import { Prerequisites, Card, InlineIcon } from "docs-ui"
 
 export const metadata = {
   title: `Use Saved Payment Methods During Checkout`,
+  keywords: [
+    "saved payment methods",
+    "stripe",
+    "payment provider",
+    "checkout",
+    "nextjs",
+  ]
 }
 
 # {metadata.title}