refactor: move profile size from img to degicated avatar shortcode (#817)

BREAKING CHANGE: The `size=profile` option was removed from the `img` shortcode. To create avatar images the new `avatar` shortcode can be used.

exampleSite/content/en/shortcodes/avatar/_index.md

@@ -0,0 +1,46 @@
+---
+title: Avatar
+resources:
+  - name: avatar
+    src: "avatar.jpg"
+    title: "Avatar"
+---
+
+The avatar shortcode is another custom image shortcode.
+
+<!--more-->
+
+## Usage
+
+Define a resource in the page front matter.
+
+<!-- spellchecker-disable -->
+
+```md
+---
+resources:
+  - name: avatar
+    src: "images/avatar.jpg"
+    title: "Avatar"
+---
+
+{{</* avatar name="avatar" */>}}
+```
+
+<!-- spellchecker-enable -->
+
+## Attributes
+
+<!-- prettier-ignore-start -->
+<!-- spellchecker-disable -->
+{{< propertylist name=shortcode-avatar sort=name order=asc >}}
+<!-- spellchecker-enable -->
+<!-- prettier-ignore-end -->
+
+## Example
+
+<!-- spellchecker-disable -->
+
+{{< avatar name=avatar size="small" >}}
+
+<!-- spellchecker-enable -->