Add .gitattribute assisted language detection to blame, diff and render (#17590)

Use check attribute code to check the assigned language of a file and send that in to
chroma as a hint for the language of the file.

Signed-off-by: Andrew Thornton <art27@cantab.net>

modules/indexer/code/search.go

@@ -101,7 +101,7 @@ func searchResult(result *SearchResult, startIndex, endIndex int) (*Result, erro
 		Language:       result.Language,
 		Color:          result.Color,
 		LineNumbers:    lineNumbers,
-		FormattedLines: highlight.Code(result.Filename, formattedLinesBuffer.String()),
+		FormattedLines: highlight.Code(result.Filename, "", formattedLinesBuffer.String()),
 	}, nil
 }