Rollup merge of #131394 - ismailarilik:fix/rustdoc/add-space-between-struct-fields-and-their-descriptions, r=GuillaumeGomez

fix(rustdoc): add space between struct fields and their descriptions

Stolen from #128541.
Fixes #128260.

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<table>
  <thead>
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      <th scope="col">Before</th>
      <th scope="col">After</th>
    </tr>
  </thead>
  <tbody>
    <tr>
      <td scope="row">
        <img
          src="https://github.com/user-attachments/assets/650c3e74-a067-492a-9ba3-557f9214f875"
        />
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        <img
          src="https://github.com/user-attachments/assets/413ef9b0-8fca-4e16-978a-7b88d05299dc"
        />
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Unlike original PR, I didn't add space between field headers; I put it between headers and descriptions. So if there are only headers, the space is not changed. Otherwise, I put a space like the space between paragraphs (.75em) which makes sense for me but feel free to adjust it or ask me to do so.

r? `@GuillaumeGomez`

Author: matthiaskrgr

src/librustdoc/html/static/css/rustdoc.css

@@ -230,6 +230,9 @@ h4.code-header {
 	padding: 0;
 	white-space: pre-wrap;
 }
+.structfield {
+	margin: 0.6em 0;
+}
 
 #crate-search,
 h1, h2, h3, h4, h5, h6,