docs: kbuild: Document search jump feature

Menuconfig has a feature where you can "press the key in the (#) prefix
to jump directly to that location. You will be returned to the current
search results after exiting this new menu."

This feature is poorly documented,
so add it to the kconfig.rst documentation.

Signed-off-by: Jesse Taube <Mr.Bossman075@gmail.com>
Acked-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

Documentation/kbuild/kconfig.rst

@@ -210,6 +210,10 @@ Searching in menuconfig:
 	first (and in alphabetical order), then come all other symbols,
 	sorted in alphabetical order.
 
+	In this menu, pressing the key in the (#) prefix will jump
+	directly to that location. You will be returned to the current
+	search results after exiting this new menu.
+
 ----------------------------------------------------------------------
 
 User interface options for 'menuconfig'
@@ -262,6 +266,10 @@ Searching in nconfig:
 	F8 (SymSearch) searches the configuration symbols for the
 	given string or regular expression (regex).
 
+	In the SymSearch, pressing the key in the (#) prefix will
+	jump directly to that location. You will be returned to the
+	current search results after exiting this new menu.
+
 NCONFIG_MODE
 ------------
 This mode shows all sub-menus in one large tree.