docs: updated extend docs after new feature

Author: imp-dance

docs/docs/Features/extending.md

@@ -13,19 +13,36 @@ const parentLoader = createLoader({
 
 const childLoader = parentLoader.extend({
     useQueries: () => ({...}),
-})
+    onError: () => <div>Error</div>,
+}).extend({
+    transform: () => ({...}),
+}).extend({
+    onLoading: () => <div>Overwritten loading...</div>,
+});
 ```
 
-It's worth mentioning that queries and transform are linked in this context, meaning that if you supply a new queries argument in the extended loader, but no transform, then you will not inherit the transform from the original loader.
-
-- Supplying just a new `useQueries` argument will result in transform being undefined in practise.
-- Supplying just a new `transform` argument will result in the new transform being ignored.
-- Supplying a new `transform` and a new `useQueries` argument will properly overwrite the existing base properties.
-
-All other properties in the loader will overwrite as expected. You can, for example, just supply a new `onLoading`, or `onError`.
-
+:::caution
 `.extend` will not merge two separate `useQueries` properties. For example, you cannot _just_ inherit the deferredQueries, you must either inherit all or none of the `useQueries` argument.
+:::
+:::tip Reusable transformers
+You can extend as many times as you'd like. You can use this feature to easily inject reusable snippets, like transformers.
+
+```typescript
+type QueryRecord = Record<string, UseQueryResult<unknown>>;
+
+export const transformData = {
+  transform: (data: {
+    queries: QueryRecord;
+    deferredQueries: QueryRecord;
+    payload: unknown;
+  }) => {
+    // handle transformation in generic way
+  },
+};
+```
+
+```typescript
+const loader = createLoader({...}).extend(transformData);
+```
 
-:::info
-You may extend _extended_ loaders, to create an inheritance model.
 :::