chore: add docs about package prefix (#144)

Author: dsinghvi

fern/products/sdks/overview/java/configuration.mdx

@@ -78,6 +78,12 @@ When enabled, generates public constructors for model types.
 </ParamField>
 
 <ParamField path="package-prefix" type="string" required={false} toc={true}>
+By default, the generated SDK will use the package prefix `com.{orgName}.api`, where `{orgName}` is your Fern organization name (defined in `fern.config.json`). 
+To override this, you can specify the `package-prefix` field in your `generators.yml` configuration.
+```
+config: 
+  package-prefix: my.new.package
+```
 </ParamField>
 
 <ParamField path="package-layout" type="'nested' | 'flat'" default="nested" required={false} toc={true}>