feat(develop): Add Relay development section

Author: Dav1dde

develop-docs/services/relay/index.mdx renamed to develop-docs/relay/index.mdx

@@ -1,15 +1,12 @@
 ---
-title: Relay
+title: Relay Development
+sidebar_order: 60
 ---
 
 Relay is a service for event filtering, rate-limiting and processing. It can act as:
 
 * the store endpoint for your Sentry installation. See [Relay developer
   documentation](https://getsentry.github.io/relay/relay/).
-
 * an additional middle layer between your application and Sentry. See [Relay product
   documentation](https://docs.sentry.io/product/relay/).
 
-## Contents
-
-* [Naming and versioning patterns in project config](/services/relay/projectconfig-versioning/)

develop-docs/services/relay/projectconfig-versioning.mdx renamed to develop-docs/relay/projectconfig-versioning.mdx

@@ -15,6 +15,7 @@ const devDocsMenuItems: {root: string; title: string; hideChevron?: boolean}[] =
   {root: 'frontend', title: 'Frontend'},
   {root: 'backend', title: 'Backend'},
   {root: 'sdk', title: 'SDK Development'},
+  {root: 'relay', title: 'Relay Development'},
   {root: 'services', title: 'Services'},
   {root: 'integrations', title: 'Integrations'},
   {root: 'self-hosted', title: 'Self-Hosted Sentry'},