markdown_preview: Fix trimming of leading whitespace in Markdown lists (#35750)

Closes #35712

Release Notes:

- Fixed white-space trimming leading to disconnect between list items
and content in markdown previews.

---------

Co-authored-by: Bennet Bo Fenner <bennetbo@gmx.de>

crates/markdown_preview/src/markdown_renderer.rs

@@ -277,7 +277,11 @@ fn render_markdown_list_item(
         .items_start()
         .children(vec![
             bullet,
-            div().children(contents).pr(cx.scaled_rems(1.0)).w_full(),
+            v_flex()
+                .children(contents)
+                .gap(cx.scaled_rems(1.0))
+                .pr(cx.scaled_rems(1.0))
+                .w_full(),
         ]);
 
     cx.with_common_p(item).into_any()