chore(demo): fix the path of picture files in readme (#3451)

demos/benchmark/README.md

@@ -33,7 +33,7 @@ In other words, the benchmark shows the FPS from the pure rendering time.
 
 By default, only the changed areas are refreshed. It means if only a few pixels are changed in 1 ms the benchmark will show 1000 FPS. To measure the performance with full screen refresh uncomment `lv_obj_invalidate(lv_scr_act())` in `monitor_cb()` in `lv_demo_benchmark.c`.
 
-![LVGL benchmark running](https://github.com/lvgl/lvgl/tree/master/demos/benchmark/screenshot1.png?raw=true)
+![LVGL benchmark running](screenshot1.png)
 
 If you are doing performance analysis for 2D image processing optimization, LCD latency (flushing data to LCD) introduced by `disp_flush()` might dilute the performance results of the LVGL drawing process, hence make it harder to see your optimization results (gain or loss). To avoid such problem, please:
 

demos/music/README.md

@@ -4,7 +4,7 @@
 The music player demo shows what kind of modern, smartphone-like user interfaces can be created on LVGL. It works the best with display with 480x272 or 272x480 resolution.
 
 
-![Music player demo with LVGL embedded GUI library](https://github.com/lvgl/lvgl/tree/master/demos/music/screenshot1.gif?raw=true)
+![Music player demo with LVGL embedded GUI library](screenshot1.gif)
 
 ## Run the demo
 - In `lv_conf.h` or equivalent places set `LV_USE_DEMO_MUSIC 1`

demos/stress/README.md

@@ -5,7 +5,7 @@
 A stress test for LVGL.
 It contains a lot of object creation, deletion, animations, styles usage, and so on. It can be used if there is any memory corruption during heavy usage or any memory leaks.
 
-![Stress demo with LVGL embedded GUI library](https://github.com/lvgl/lvgl/tree/master/demos/stress/screenshot1.gif?raw=true)
+![Stress demo with LVGL embedded GUI library](screenshot1.gif)
 
 ## Run the demo
 - In `lv_conf.h` or equivalent places set `LV_USE_DEMO_STRESS 1`