Add example for different data sources in README

Added example of fetching users from different sources.

Author: monokkai

README.md

@@ -64,6 +64,16 @@ const users = await mockmate({
 });
 ```
 
+### Different sources
+
+```ts
+  const users = await mockmate({
+    category: "users",
+    source: "fakestoreapi", // source: "jsonplaceholder"
+    quantity: 2,
+  });
+```
+
 ### Generate Schema
 
 ```ts