fix: always use image icon for image links, regardless of URL type

[twio142]

This PR fixes an issue where image links (![alt](...)) do not consistently display the image icon.

Currently, the plugin assigns icons based on the link target:

• Local image paths correctly use the image icon
• Image links pointing to web URLs (e.g. https://...) are treated as normal web links and get the web URL icon instead

I personally think that image links should always display the image icon, regardless of the URL type.