grammars: Highlight markdown code spans in tables (#57506)

Resolves https://github.com/zed-industries/zed/issues/57501

This diff fixes Markdown inline syntax highlighting inside pipe table
cells. The block Markdown parser represents table content as
`pipe_table_cell` nodes rather than `inline` nodes, so Zed’s existing
`markdown-inline` injection ran for paragraph text but skipped code
spans inside tables.

With this change, table cells also inject `markdown-inline`, allowing
existing inline highlighting to handle code spans consistently between
paragraph text and table cells.

| Before | After |
| --- | --- |
| <img width="500" alt="Before screenshot"
src="https://github.com/user-attachments/assets/bdb75c18-9f20-4f3c-bea6-946194098db6"
/> | <img width="500" alt="After screenshot"
src="https://github.com/user-attachments/assets/23ae7bc5-5208-4dc7-ab6f-d07404aeae06"
/> |

Release Notes:

- Fixed Markdown inline code highlighting in table cells.

crates/grammars/src/markdown/injections.scm

@@ -6,6 +6,9 @@
 ((inline) @injection.content
   (#set! injection.language "markdown-inline"))
 
+((pipe_table_cell) @injection.content
+  (#set! injection.language "markdown-inline"))
+
 ((html_block) @injection.content
   (#set! injection.language "html"))