feat(lib) add ffmpeg video and image decoder (#2805)

* add ffmpeg decoder to extra/libs

* fix(Kconfig) add ffmpeg configuration

Signed-off-by: pengyiqiang <pengyiqiang@xiaomi.com>

* feat(example) add ffmpeg decoder example

Signed-off-by: pengyiqiang <pengyiqiang@xiaomi.com>

* update lv_conf_template.h

* feat(example) add picture and video to ffmpeg example

* docs(libs) update FFMpeg introduction

Signed-off-by: pengyiqiang <pengyiqiang@xiaomi.com>

* fix(ffmpeg) replace with new videos and examples

Signed-off-by: pengyiqiang <pengyiqiang@xiaomi.com>

* fix(ffmpeg) remove the include of lv_img_cache.h

* fix(ffmpeg) add LV_ASSERT_OBJ

* Update examples/libs/ffmpeg/lv_example_ffmpeg_2.c

Co-authored-by: pengyiqiang <pengyiqiang@xiaomi.com>
Co-authored-by: Gabor Kiss-Vamosi <kisvegabor@gmail.com>

examples/libs/ffmpeg/lv_example_ffmpeg.h

@@ -0,0 +1,39 @@
+/**
+ * @file lv_example_ffmpeg.h
+ *
+ */
+
+#ifndef LV_EXAMPLE_FFMPEG_H
+#define LV_EXAMPLE_FFMPEG_H
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/*********************
+ *      INCLUDES
+ *********************/
+
+/*********************
+ *      DEFINES
+ *********************/
+
+/**********************
+ *      TYPEDEFS
+ **********************/
+
+/**********************
+ * GLOBAL PROTOTYPES
+ **********************/
+void lv_example_ffmpeg_1(void);
+void lv_example_ffmpeg_2(void);
+
+/**********************
+ *      MACROS
+ **********************/
+
+#ifdef __cplusplus
+} /*extern "C"*/
+#endif
+
+#endif /*LV_EXAMPLE_FFMPEG_H*/