feat: Sort (markdown) output by file path

[mahlzahn]

Currently, each run of lychee sorts the files where broken links are found in another kind of random order. That makes it difficult to compare different outputs.

I suggest to let lychee by default sort the headings of the output.

(A workaround is to do it manually afterwards, but it would be nice to have it inside lychee)

[mre]

Good idea.

The content is in a data structure called error_map, which is not sorted (beause it's a HashMap).
We iterate over the error_map in multiple places, dependening on the output format:

lychee/lychee-bin/src/formatters/stats/markdown.rs

Lines 128 to 136 in 3fb94e0

	if !&map.is_empty() {
	writeln!(f, "\n## {name} per input")?;
	for (source, responses) in map {
	writeln!(f, "\n### {name} in {source}\n")?;
	for response in responses {
	writeln!(f, "{}", write_stat(response)?)?;
	}
	}
	}

lychee/lychee-bin/src/formatters/stats/compact.rs

Lines 40 to 48 in 3fb94e0

	for (source, responses) in &stats.error_map {
	color!(f, BOLD_YELLOW, "[{}]:\n", source)?;
	for response in responses {
	writeln!(
	f,
	"{}",
	response_formatter.format_detailed_response(response)
	)?;
	}

lychee/lychee-bin/src/formatters/stats/detailed.rs

Lines 52 to 74 in 3fb94e0

	for (source, responses) in &stats.error_map {
	// Using leading newlines over trailing ones (e.g. `writeln!`)
	// lets us avoid extra newlines without any additional logic.
	write!(f, "\n\nErrors in {source}")?;
	for response in responses {
	write!(
	f,
	"\n{}",
	response_formatter.format_detailed_response(response)
	)?;
	if let Some(suggestions) = &stats.suggestion_map.get(source) {
	writeln!(f, "\nSuggestions in {source}")?;
	for suggestion in *suggestions {
	writeln!(f, "{suggestion}")?;
	}
	}
	}
	}
	Ok(())
	}

The proper way to change this would be to return the error_map sorted by key. We could add a helper method, e.g. sorted_error_map to the stats and use that in the above places instead of directly iterating over error_map.

I'd be thankful for a pull request if anyone wants to tackle this. Should be pretty straightforward.