feat(font): add imgfont - can be used to add emojis to label/span (#3160)

* feature(font): draw img in label/span

* add to tests

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

docs/others/imgfont.md

@@ -0,0 +1,29 @@
+```eval_rst
+.. include:: /header.rst 
+:github_url: |github_link_base|/others/imgfont.md
+```
+## Image font (imgfont)
+Draw image in label or span obj with imgfont.
+This is often used to display Unicode emoji icons in text.
+Supported image formats: determined by LVGL image decoder.
+
+## Usage
+Enable `LV_USE_IMGFONT` in `lv_conf.h`.
+
+To create a new imgfont use `lv_imgfont_create(height, path_cb)`.
+
+`height` used to indicate the size of a imgfont.
+`path_cb` Used to get the image path of the specified unicode.
+
+Use `lv_imgfont_destroy(imgfont)` to destroy a imgfont that is no longer used.
+
+## Example
+```eval_rst
+.. include:: ../../examples/others/imgfont/index.rst
+```
+
+## API
+```eval_rst
+.. doxygenfile:: lv_imgfont.h
+  :project: lvgl
+```