update plugin readme

Author: brijr

plugin/README.md

@@ -17,7 +17,7 @@ After installing and activating the plugin:
 
 1. Go to Settings > Next.js Revalidation in your WordPress admin
 2. Enter your Next.js site URL (without trailing slash)
-3. Create a secure webhook secret (a random string)
+3. Create a secure webhook secret (a random string), you can use `openssl rand -base64 32` to generate one
 4. Save your settings
 
 ### 2. Next.js Environment Variables
@@ -50,4 +50,4 @@ If revalidation isn't working:
 1. Check that your Next.js URL is correct in the plugin settings
 2. Verify the webhook secret matches in both WordPress and Next.js
 3. Check your server logs for any errors in the API route
-4. Enable notifications in the plugin settings to see revalidation status
+4. Enable notifications in the plugin settings to see revalidation status