Update next.mdx to indicate the configuration file.

I'm new using tailwind so I waste time to know the configuration file. 

Thanks to this video see I learned where to do it.
https://www.youtube.com/watch?v=jpfuHjsxFZU

Author: i0n-

documentation/react/guide/next.mdx

@@ -87,7 +87,7 @@ pnpm i @material-tailwind/react
 
 <span id="tailwindcss-config" className="scroll-mt-48" />
 
-Once you install @material-tailwind/react you need to wrap your tailwind css configurations with the <Code>withMT()</Code> function coming from @material-tailwind/react/utils.
+Once you install @material-tailwind/react you need to wrap your tailwind css configurations with the <Code>withMT()</Code> function coming from @material-tailwind/react/utils on the <Code>tailwind.config.js</Code> file.
 
 ```js {1, 3, 9}
 const withMT = require("@material-tailwind/react/utils/withMT");