Clearer verification of installation (#6764)

* Clearer verification of installation

Increase the clarity of the installation process by downloading the model used in the verification sample code.

* Fix spelling mistake

Foxed spelling mistake in verification subsection

Co-authored-by: RangiLyu <[email protected]>

Co-authored-by: RangiLyu <[email protected]>

Author: zactodd

docs/en/get_started.md

@@ -229,7 +229,11 @@ PYTHONPATH="$(dirname $0)/..":$PYTHONPATH
 
 ## Verification
 
-To verify whether MMDetection is installed correctly, we can run the following sample code to initialize a detector and inference a demo image.
+To verify whether MMDetection is installed correctly, we can run the following sample code to initialize a detector and inference a demo image, but first we need to download config and checkpoint files.
+
+```shell
+mim download mmdet --config faster_rcnn_r50_fpn_1x_coco --dest .
+```
 
 ```python
 from mmdet.apis import init_detector, inference_detector