docs(examples): introduce summary and description to examples (#9968)

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

examples/libs/svg/about.md

@@ -0,0 +1,6 @@
+---
+title: "SVG"
+order: 15
+---
+
+LVGL's built-in SVG parser and renderer for scalable vector graphics. Enable with `LV_USE_SVG` in `lv_conf.h`.

examples/libs/svg/lv_example_svg_1.c

@@ -3,7 +3,14 @@
 #if LV_USE_SVG && LV_USE_VECTOR_GRAPHIC
 
 /**
- * Load an SVG from data
+ * @title SVG from inline markup
+ * @brief Render an SVG circle described by a literal string as an image source.
+ *
+ * A static `lv_image_dsc_t` is populated with `LV_IMAGE_HEADER_MAGIC`, a
+ * 450x150 display size, and a pointer to the literal SVG markup drawing
+ * a red circle with a blue stroke. The descriptor is handed to
+ * `lv_image_set_src` on an image widget placed on the active screen so
+ * the SVG decoder renders the markup on demand.
  */
 void lv_example_svg_1(void)
 {

examples/libs/svg/lv_example_svg_2.c

@@ -3,7 +3,12 @@
 #if LV_USE_SVG && LV_USE_VECTOR_GRAPHIC
 
 /**
- * Load an SVG from a file
+ * @title SVG from filesystem
+ * @brief Load an SVG file through the LVGL filesystem and use it as an image source.
+ *
+ * An image widget is created on the active screen and its source is set to
+ * `A:lvgl/examples/assets/circle.svg`, so the SVG decoder reads the file
+ * through the filesystem driver registered under drive letter `A`.
  */
 void lv_example_svg_2(void)
 {

examples/libs/svg/lv_example_svg_3.c

@@ -16,6 +16,16 @@ static void event_cb(lv_event_t * e)
     lv_svg_node_delete(svg);
 }
 
+/**
+ * @title Draw SVG in a draw event
+ * @brief Paint SVG markup directly into the screen's draw layer on `LV_EVENT_DRAW_MAIN`.
+ *
+ * `lv_obj_add_event_cb` subscribes a handler to the active screen's
+ * `LV_EVENT_DRAW_MAIN`. The handler parses an inline SVG string with
+ * `lv_svg_load_data`, calls `lv_draw_svg` against the layer returned by
+ * `lv_event_get_layer`, and then releases the node with
+ * `lv_svg_node_delete`.
+ */
 void lv_example_svg_3(void)
 {
     lv_obj_add_event_cb(lv_screen_active(), event_cb, LV_EVENT_DRAW_MAIN, NULL);