docs(animimg) Add missing animation image page (#2609)

* docs(animimg) Add missing animation image page

Skeleton page for the new `animimg` object.
It needs more review and updating, but this can serve as a start.

* docs(examples) Add index.rst for animation image

Add index.rst for animation image to include the example in the documentation of the widget.

* Update animimg.md

docs/widgets/extra/animimg.md

@@ -0,0 +1,53 @@
+```eval_rst
+.. include:: /header.rst 
+:github_url: |github_link_base|/widgets/animimg.md
+```
+# Animation Image (lv_animimg)
+
+## Overview
+
+The animation image is similar to the norlmal 'Image' object. The only difference is that instead of one source image, you set an array of multiple source images.
+
+You can specify a duration and repeat count.
+
+
+## Parts and Styles
+- `LV_PART_MAIN` A background rectangle that uses the typical background style properties and the image itself using the image style properties.
+ 
+
+## Usage
+
+### Image sources
+To set the image in a state, use the `lv_animimg_set_src(imgbtn, dsc[], num)`.
+ 
+
+## Events
+No special events are sent by image objects.
+
+See the events of the Base object too.
+
+Learn more about [Events](/overview/event).
+
+
+## Keys
+No Keys are processed by the object type.
+
+Learn more about [Keys](/overview/indev).
+
+
+## Example
+
+```eval_rst
+
+.. include:: ../../../examples/widgets/animimg/index.rst
+
+```
+
+## API
+
+```eval_rst
+
+.. doxygenfile:: lv_animimg.h
+  :project: lvgl
+
+```

examples/widgets/animimg/index.rst

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+
+Simple Animation Image 
+""""""""""""""""
+
+.. lv_example:: widgets/animimg/lv_example_animimg_1.c 
+  :language: c
+  :description: A simple example to demonstrate the use of an animation image.