Nive JSON comments in Cedar policy example above the example

Remove inline // comments from JSON code block as they are invalid
JSON syntax and will cause parsing errors. Move explanations to
bullet points above the example for better clarity.

Author: jhrozek

docs/toolhive/_partials/_basic-cedar-config.mdx

@@ -1,19 +1,22 @@
-Create a JSON or YAML file with Cedar policies. Here's an example in JSON
-format:
+Create a JSON or YAML file with Cedar policies. This example demonstrates
+several policy patterns:
+
+- Allow everyone to use the weather tool
+- Restrict admin_tool to a specific user (alice123)
+- Role-based access: only users with the 'premium' role can call any tool
+- Attribute-based: allow calculator tool only for add/subtract operations
+
+Here's an example in JSON format:
 
 ```json
 {
   "version": "1.0",
   "type": "cedarv1",
   "cedar": {
     "policies": [
-      // Allow everyone to use the weather tool
       "permit(principal, action == Action::\"call_tool\", resource == Tool::\"weather\");",
-      // Restrict admin_tool to a specific user
       "permit(principal == Client::\"alice123\", action == Action::\"call_tool\", resource == Tool::\"admin_tool\");",
-      // Role-based access: only users with the 'premium' role can call any tool
       "permit(principal, action == Action::\"call_tool\", resource) when { principal.claim_roles.contains(\"premium\") };",
-      // Attribute-based: allow calculator tool only for add/subtract operations
       "permit(principal, action == Action::\"call_tool\", resource == Tool::\"calculator\") when { resource.arg_operation == \"add\" || resource.arg_operation == \"subtract\" };"
     ],
     "entities_json": "[]"