docs: Update nuxt3 usage

docs: update nuxt3 usage

Author: CodeDredd

README.md

@@ -73,7 +73,7 @@ import { useCompression } from 'h3-compression'
 
 export default defineNitroPlugin((nitro) => {
   nitro.hooks.hook('render:response', async (response, { event }) => {
-    if (!response.headers?.['content-type'].startsWith('text/html'))
+    if (!response.headers?.['content-type']?.startsWith('text/html'))
       return
 
     await useCompression(event, response)