docs: mention `SINGLE_INSTANCE_SERVER`

.env.example

@@ -1,5 +1,6 @@
 NUXT_PUBLIC_TRANSLATE_API=
 NUXT_PUBLIC_DEFAULT_SERVER=
+SINGLE_INSTANCE_SERVER=
 NUXT_PUBLIC_PRIVACY_POLICY_URL=
 
 # Production only

docs/content/2.deployment/1.netlify.md

@@ -45,6 +45,7 @@ There are 5 environment variables to add.
 | NUXT_CLOUDFLARE_NAMESPACE_ID | This is your CloudFlare KV Namespace ID. You can find it in "Workers > KV". |
 | NUXT_STORAGE_DRIVER | Because we're using CloudFlare, we'll need to set this to `cloudflare`. |
 | NUXT_PUBLIC_DEFAULT_SERVER | This is the address of the Mastodon instance that will show up when a user visits your Elk deployment and is not logged in. If you don't make that variable, it will point to `m.webtoo.ls` by default. |
+| SINGLE_INSTANCE_SERVER | This can't be set at runtime, but if enabled at build-time it will disable signing in to servers other than the server specified in `NUXT_PUBLIC_DEFAULT_SERVER` |
 | NUXT_PUBLIC_PRIVACY_POLICY_URL | This is the URL to a web page with information on your privacy policy. |
 
 That's it! All that's left to do is...