Consecutive occurences of examples lead to empty `DetailsBlock`s in `docs.json`

[YDX-2147483647]

Description

Consecutive occurences of examples lead to DetailsBlock::Html("") in docs.json:

{
  "kind": "html",
  "content": ""
}

This doesn't affect the official docs, but it causes styling difficulties for downstream projects. For instance, if the downstream project wraps each content with a <div>, then this empty <div> will prevent margins of sibling HTML elements to collapse, resulting in awkward additional spaces.

I suggest removing those empty DetailsBlocks.

Example

For example, there're two consecutive examples in par.line.numbering:

typst/crates/typst-library/src/model/par.rs

Lines 746 to 767 in 16de17a

	/// How to number each line. Accepts a
	/// [numbering pattern or function]($numbering) taking a single number.
	///
	/// ```example
	/// >>> #set page(margin: (left: 3em))
	/// #set par.line(numbering: "I")
	///
	/// Roses are red. \
	/// Violets are blue. \
	/// Typst is there for you.
	/// ```
	///
	/// ```example
	/// >>> #set page(width: 200pt, margin: (left: 3em))
	/// #set par.line(
	/// numbering: i => if calc.rem(i, 5) == 0 or i == 1 { i },
	/// )
	///
	/// #lorem(60)
	/// ```
	#[ghost]
	pub numbering: Option<Numbering>,

After parsing, its doc comment becomes the following in docs.json.

                        "details": [
                          {
                            "kind": "html",
                            "content": "<p>How to number each line. Accepts a\n<a href=\"/reference/model/numbering/\">numbering pattern or function</a> taking a single number.</p>"
                          },
                          {
                            "kind": "example",
                            "content": {
                              "body": "<div class=\"previewed-code\">…</div>",
                              "title": null
                            }
                          },
                          {
                            "kind": "html",
                            "content": "" // 👈 Here is empty
                          },
                          {
                            "kind": "example",
                            "content": {
                              "body": "<div class=\"previewed-code\">…</div>",
                              "title": null
                            }
                          }
                        ],

You can inspect the full json of this page at https://typst-docs-web.netlify.app/en-us-v0.14.0/reference/model/par/index.json.

All examples:

$ jq '.. | select(type == "object" and has("details") and (.details|type) == "array") | { name: .name, details: [.details[] | select((.content | type) == "string" and .content == "")] } | select(.details | length > 0)' docs.json --compact-output
{"name":"match","details":[{"kind":"html","content":""}]}
{"name":"numbering","details":[{"kind":"html","content":""}]}
{"name":"style","details":[{"kind":"html","content":""},{"kind":"html","content":""}]}
{"name":"augment","details":[{"kind":"html","content":""}]}
{"name":"stroke","details":[{"kind":"html","content":""}]}

Cause

I guess we should check if docs[i..fence_idx].trim() is empty here:

typst/docs/src/lib.rs

Lines 574 to 577 in 16de17a

	// First, push non-fenced content.
	if found > 0 {
	res.push(RawDetailsBlock::Markdown(&docs[i..fence_idx]));
	}

(RawDetailsBlock::Markdown will turn into DetailsBlock::Html later.)