docs: improve custom field docs (#50)

docs/catalyst/admin/types.md

@@ -12,10 +12,48 @@ There are two default ticket types: `Alert` and `Incident`, but you can add more
 
 ## Fields
 
-- **singular**: The singular name of the ticket type.
-- **plural**: The plural name of the ticket type.
-- **icon**: The icon of the ticket type. You can use [Lucide icons](https://lucide.dev/icons/),
-  but need to convert the icon name to camelCase, e.g. `flask-conical` becomes `FlaskConical`
-- **schema**: The schema of the ticket type. The schema is used to generate the details form for the ticket type.
-  You need use the [JSON Schema](https://json-schema.org/) format to define the schema,
-  but currently only string properties are supported.
+### `singular` and `plural` Fields
+
+The `singular` and `plural` fields are used to define the name of the ticket type.
+
+### `icon` Field
+
+The `icon` field is used to define the icon of the ticket type.
+You can use [Lucide icons](https://lucide.dev/icons/),
+but need to convert the icon name to camelCase, e.g. `flask-conical` becomes `FlaskConical`
+
+### `schema` Field
+
+The `schema` field is used to define the custom fields for details of the ticket type.
+It uses a subset of the [JSON Schema](https://json-schema.org/) format to define the schema,
+currently enum, boolean, string, and integer properties are supported without any additional constraints.
+
+The following example shows a schema with the four different property types:
+
+```json
+{
+  "type": "object",
+  "properties": {
+    "severity": {
+      "type": "string",
+      "enum": [
+        "Low",
+        "Medium",
+        "High"
+      ]
+    },
+    "false_positive": {
+      "type": "boolean",
+      "title": "False Positive"
+    },
+    "source": {
+      "type": "string",
+      "title": "Source"
+    },
+    "affected_user_count": {
+      "type": "integer",
+      "title": "Affected User Count"
+    }
+  }
+}
+```