Request: Remove hard-coded margins, padding

[tobydriscoll]

It looks as though Format.jl sets the CSS border, margins, and padding of a pre.hljl selector using hard-coded values. In my testing, a theme cannot override these settings. This complicates downstream usage. Most saliently, the caller cannot set them in the pre selector for itself and have those values respected across a variety of containers. (See JunoLab/Weave.jl#172 (comment).)

Options would be to remove these values from the pre.hljl selector in Format.jl, or make the values changeable via the theme.

[mortenpi]

I agree that hard-coded values in the CSS are not ideal. If nothing else, we could make it configurable, so that you can override the values or have a way of opting out of creating the pre.hljl block here:

Highlights.jl/src/Format.jl

Lines 96 to 105 in 1f498a6

	function render(io::IO, mime::MIME"text/css", theme::Theme)
	print(io,
	"""
	pre.hljl {
	border: 1px solid #ccc;
	margin: 5px;
	padding: 5px;
	overflow-x: auto;
	"""
	)