docs: more React 18 examples

docs/migration/v12.md

@@ -156,6 +156,46 @@ it('should provide the org unit data', async () => {
 })
 ```
 
+In some cases, `renderHookResult.waitFor` can just be removed and doesn't need replacing:
+
+```diff
+it('should update validationToRefresh', async () => {
+-   const { result, waitFor } = renderHook(useValidationStore)
++   const { result } = renderHook(useValidationStore)
+
+    act(() => {
+        result.current.setValidationToRefresh(true)
+    })
+
+-   await waitFor(() => {
+-       expect(result.current.getValidationToRefresh()).toBe(true)
+-   })
++   expect(result.current.getValidationToRefresh()).toBe(true)
+})
+```
+
+And testing errors:
+
+```diff
+it('throws an error when passing both a client- and a serverDate', async () => {
+    const clientDate = new Date('2022-10-13 10:00:00')
+    const serverDate = new Date('2022-10-13 08:00:00')
+-   const { result } = renderHook(() =>
+-       useClientServerDate({ clientDate, serverDate })
+-   )
+-   expect(result.error).toEqual(
+-       new Error(
+-           '`useClientServerDate` does not accept both a client and a server date'
+-       )
+
++  expect(() => {
++       renderHook(() => useClientServerDate({ clientDate, serverDate }))
++   }).toThrow(
++       '`useClientServerDate` does not accept both a client and a server date'
++   )
+})
+```
+
 ##### Fake timers
 
 Faking timers can help with tests that seem to fail with concurrency issues: