patch 8.2.3664: cannot adjust sign highlighting for 'cursorline'

Problem:    Cannot adjust sign highlighting for 'cursorline'.
Solution:   Add CursorLineSign and CursorLineFold highlight groups.
            (Gregory Anders, closes #9201)
diff --git a/runtime/doc/syntax.txt b/runtime/doc/syntax.txt
index db0f70f..08d3f5f 100644
--- a/runtime/doc/syntax.txt
+++ b/runtime/doc/syntax.txt
@@ -5251,6 +5251,10 @@
 							*hl-CursorLineNr*
 CursorLineNr	Like LineNr when 'cursorline' is set and 'cursorlineopt'
 		contains "number" or is "both", for the cursor line.
+							*hl-CursorLineSign*
+CursorLineSign	Like SignColumn when 'cursorline' is set for the cursor line.
+							*hl-CursorLineFold*
+CursorLineFold	Like FoldColumn when 'cursorline' is set for the cursor line.
 							*hl-MatchParen*
 MatchParen	The character under the cursor or just before it, if it
 		is a paired bracket, and its match. |pi_paren.txt|