Copy / paste or upload an an image without a image extension (.png,.gif etc ...) is treated as a link

**Is your feature request related to a problem? Please describe.**
I am using Appwrite as backend. Appwrite provides a storage engine that allows you to store any files. To retrieve them the link is something like [domain/project/view?id=8989890809

When pasting an image, I am using Appwrite to store it then retrieve the generated link which is passed to EasyMDE. EasyMDE considers it as link since there is no extension it recognized.

**Describe the solution you'd like**
2 solutions: one being less painful :smile:

Solution 1 (the painful one): EasyMDE is fetching the content to use its mime-type and make the proper decision about whether this is an image

Solution 2 : being able to call the success callback function from the imageUploadFunction with a additional parameter to specify that this is an image . i.e : instead of onSucces(url) -> onSuccess(url,thisIsAnImage)

Solution 3 : anything better :)

Start by tracing imageUploadFunction and the logic that decides whether a pasted or uploaded URL is an image. Compare the requested MIME-type lookup and callback metadata approaches, then check existing image-upload behavior. Done means image URLs without filename extensions are handled as images without breaking ordinary links.

Written by the indexing model from the issue text.