Replace pillow dependency with filetype

[cilki]

Fixes #1801

[github-actions]

Label error. Requires exactly 1 of: bug, enhancement, major, minor, patch, skip-changelog. Found:

[adehad]

I'm concerned by the current maintained state of filetype but it appears that for images at least we should be fine. I am concerned that we don't have a test for this method yet, so if we can add one in that would give me confidence in using this package

[dimitarOnGithub]

@adehad just in case you've missed it, there's some general conversation about the use of this functionality going on in #1867 around this, seems like that was the PR that got traction, even if it was filed after this one.