markdown: Fix horizontal rules and blockquotes not visible (#53223)

Smit Barmase created

Closes #53167

Self-Review Checklist:

- [x] I've reviewed my own diff for quality, security, and reliability
- [x] Unsafe blocks (if any) have justifying comments
- [x] The content is consistent with the [UI/UX
checklist](https://github.com/zed-industries/zed/blob/main/CONTRIBUTING.md#uiux-checklist)
- [ ] Tests cover the new/changed behavior
- [x] Performance impact has been considered and is acceptable

Release Notes:

- Fixed horizontal rules and blockquotes not being visible in the
Markdown preview.

Change summary

crates/markdown/src/markdown.rs | 2 ++
1 file changed, 2 insertions(+)

Detailed changes

crates/markdown/src/markdown.rs 🔗

@@ -154,6 +154,8 @@ impl MarkdownStyle {
             base_text_style: text_style.clone(),
             syntax: cx.theme().syntax().clone(),
             selection_background_color: colors.element_selection_background,
+            rule_color: colors.border,
+            block_quote_border_color: colors.border,
             code_block_overflow_x_scroll: true,
             heading_level_styles: Some(HeadingLevelStyles {
                 h1: Some(TextStyleRefinement {