chore: forgot to mention the verification record

Author: orangci

src/guides/vercel.md

@@ -15,7 +15,7 @@ If you haven't made a Vercel site, make sure to make one. Follow the instruction
 ### Creating the domain
 
 1. Navigate to your Vercel dashboard. Then, navigate to the "Domains" tab of your project's settings. Click "Add Domain" and enter the is-a.dev subdomain you want (e.g. `example.is-a.dev`). 
-2. Once you're past the "Configure Environment and Redirects" tab—if unsure, just click "Save"—then click "Continue manually".
+2. Once you're past the "Configure Environment and Redirects" tab—if unsure, just click "Save"—then click "Continue manually". Copy the TXT verification value that you'll get; you'll need this in step 4.
 3. Fork our [repository](https://github.com/is-a-dev/register) and create a file **in the `/domains` folder** named `your-domain.json`. Replace `your-domain` with the name of the subdomain you chose earlier in the Vercel dashboard.
 4. In this file, paste the following JSON and ***make sure to replace all the values properly***, except for the CNAME, which you should leave untouched.