patch 8.2.4724: current instance of last search pattern not easily spotted

Problem:    Current instance of last search pattern not easily spotted.
Solution:   Add CurSearch highlighting. (closes #10133)
diff --git a/runtime/doc/syntax.txt b/runtime/doc/syntax.txt
index 826a0b4..dfb0fb7 100644
--- a/runtime/doc/syntax.txt
+++ b/runtime/doc/syntax.txt
@@ -5318,6 +5318,8 @@
 							*hl-Search*
 Search		Last search pattern highlighting (see 'hlsearch').
 		Also used for similar items that need to stand out.
+							*hl-CurSearch*
+CurSearch	Current match for the last search pattern (see 'hlsearch').
 							*hl-SpecialKey*
 SpecialKey	Meta and special keys listed with ":map", also for text used
 		to show unprintable characters in the text, 'listchars'.