Markdown preview image rendering

[mikayla-maki]

Closes #13246

Supersedes: #16192

I couldn't push to the git fork this user was using, so here's the exact same PR but with some style nits implemented.

Release Notes:

• Added image rendering to the Markdown preview

[FireFingers21]

This is awesome! Just tried it out in the 0.164.2 stable release. The only issue I can see is that the images don't scale. For example, I have a really wide image that I can only see half of in the preview. Resizing the window makes it worse as text wraps correctly, but the image just gets cropped.

[fasterthanlime]

Happy to see this land — are the supported image types documented anywhere? I use JPEG-XL when authoring Markdown, which is otherwise supported by macOS, Safari, etc. — would be super neat if it ended up being supported in Zed too!

[uncenter]

Happy to see this land — are the supported image types documented anywhere? I use JPEG-XL when authoring Markdown, which is otherwise supported by macOS, Safari, etc. — would be super neat if it ended up being supported in Zed too!

Seeing as it uses gpui::ImageSource, I think this is the list (of extensions) that it supports:

zed/crates/gpui/src/elements/img.rs

Lines 201 to 210 in 6ebd6c2

	impl Img {
	/// A list of all format extensions currently supported by this img element
	pub fn extensions() -> &'static [&'static str] {
	// This is the list in [image::ImageFormat::from_extension] + `svg`
	&[
	"avif", "jpg", "jpeg", "png", "gif", "webp", "tif", "tiff", "tga", "dds", "bmp", "ico",
	"hdr", "exr", "pbm", "pam", "ppm", "pgm", "ff", "farbfeld", "qoi", "svg",
	]
	}
	}

[uncenter]

And going off of the comment in that snippet referring to image::ImageFormat, see image-rs/image#1765.