hide empty custom codes files, hide cust showcase files in language sections

Author: devalog

fern/products/sdks/sdks.yml

@@ -20,6 +20,7 @@ navigation:
             path: ./overview/typescript/custom-code.mdx
           - link: Customer Showcase
             href: https://buildwithfern.com/showcase
+            hidden: true
       - section: Python
         contents:
           - page: Quickstart
@@ -35,6 +36,7 @@ navigation:
             path: ./overview/python/custom-code.mdx  
           - link: Customer Showcase
             href: https://buildwithfern.com/showcase
+            hidden: true
       - section: Go
         contents:
           - page: Quickstart
@@ -50,6 +52,7 @@ navigation:
             path: ./overview/go/custom-code.mdx  
           - link: Customer Showcase
             href: https://buildwithfern.com/showcase
+            hidden: true
       - section: Java
         contents:
           - page: Quickstart
@@ -65,6 +68,7 @@ navigation:
             path: ./overview/java/custom-code.mdx
           - link: Customer Showcase
             href: https://buildwithfern.com/showcase
+            hidden: true
       - section: .NET
         contents:
           - page: Quickstart
@@ -78,8 +82,10 @@ navigation:
             path: ./overview/dotnet/publishing-to-nuget.mdx
           - page: Adding custom code
             path: ./overview/dotnet/custom-code.mdx
+            hidden: true
           - link: Customer Showcase
             href: https://buildwithfern.com/showcase
+            hidden: true
       - section: PHP
         contents:
           - page: Quickstart
@@ -93,8 +99,10 @@ navigation:
             path: ./overview/php/publishing-to-packagist.mdx
           - page: Adding custom code
             path: ./overview/php/custom-code.mdx
+            hidden: true
           - link: Customer Showcase
             href: https://buildwithfern.com/showcase
+            hidden: true
       - section: Ruby
         contents:
           - page: Quickstart
@@ -108,8 +116,10 @@ navigation:
             path: ./overview/ruby/publishing-to-rubygems.mdx
           - page: Adding custom code
             path: ./overview/ruby/custom-code.mdx
+            hidden: true
           - link: Customer Showcase
             href: https://buildwithfern.com/showcase
+            hidden: true
   - section: Guides
     contents:    
       - page: Customize Method Names