Refactor network and security sections

Author: jhutchings1

src/content/docs/fundamentals/reference/connection-limits.mdx renamed to src/content/docs/fundamentals/features/network/reference/connection-limits.mdx

@@ -0,0 +1,12 @@
+---
+pcx_content_type: navigation
+title: reference
+sidebar:
+  order: 2
+  group:
+    hideIndex: true
+---
+
+import { DirectoryListing } from "~/components";
+
+<DirectoryListing />

src/content/docs/fundamentals/features/network/reference/index.mdx

@@ -0,0 +1,12 @@
+---
+pcx_content_type: navigation
+title: Reference
+sidebar:
+  order: 5
+  group:
+    hideIndex: true
+---
+
+import { DirectoryListing } from "~/components";
+
+<DirectoryListing />