Update error callout in placeholders documentation with version check and PlaceholderAPI link

Author: NonSwag

content/docs/serviceio/placeholders.mdx

@@ -109,11 +109,11 @@ current-bank: "Your current bank: %serviceio_bank%"
 
 <Callout type="error" title="Placeholder Not Working?">
   Ensure that:
-  1. ServiceIO v2.3.0+ is installed
-  2. PlaceholderAPI is installed and enabled
+  1. ServiceIO v2.3.0+ is installed (`/version ServiceIO`)
+  2. [PlaceholderAPI](https://modrinth.com/project/lKEzGugV) is installed and enabled
   3. The relevant service provider (economy, permissions...) is installed and working
-  4. ServiceIO has successfully detected and registered the service provider
-  5. There is no typo in the placeholder and it is properly used `%serviceio_<placeholder>%`
+  4. ServiceIO has successfully detected the service provider (`/service info`)
+  5. There is no typo in the placeholder and it is properly used (`%serviceio_<placeholder>%`)
 </Callout>
 
 If a placeholder shows the literal placeholder text instead of the expected value, check your ServiceIO configuration and ensure the appropriate service providers are properly installed and configured.