vim-patch:8.2.4820: not simple programmatic way to find a specific mapping

Problem:    Not simple programmatic way to find a specific mapping.
Solution:   Add getmappings(). (Ernie Rael, closes vim/vim#10273)

659c240cf7

Co-authored-by: Ernie Rael <errael@raelity.com>

runtime/doc/builtin.txt

@@ -2612,6 +2612,16 @@ getloclist({nr} [, {what}])                                       *getloclist()*
 			echo getloclist(5, {'filewinid': 0})
 <
 
+getmappings()                                                    *getmappings()*
+		Returns a |List| of all mappings.  Each List item is a |Dict|,
+		the same as what is returned by |maparg()|, see
+		|mapping-dict|.
+
+		Example to show all mappings with "MultiMatch" in rhs: >
+			echo getmappings()->filter({_, m ->
+				\ match(get(m, 'rhs', ''), 'MultiMatch') >= 0
+				\ })
+
 getmarklist([{buf}])                                             *getmarklist()*
 		Without the {buf} argument returns a |List| with information
 		about all the global marks. |mark|
@@ -4161,7 +4171,7 @@ maparg({name} [, {mode} [, {abbr} [, {dict}]]])                       *maparg()*
 
 		When {dict} is there and it is |TRUE| return a dictionary
 		containing all the information of the mapping with the
-		following items:
+		following items:			*mapping-dict*
 		  "lhs"	     The {lhs} of the mapping as it would be typed
 		  "lhsraw"   The {lhs} of the mapping as raw bytes
 		  "lhsrawalt" The {lhs} of the mapping as raw bytes, alternate

runtime/doc/usr_41.txt

@@ -1012,6 +1012,7 @@ Mappings and Menus:			    *mapping-functions*
 	digraph_getlist()	get all |digraph|s
 	digraph_set()		register |digraph|
 	digraph_setlist()	register multiple |digraph|s
+	getmappings()		get list of all mappings
 	hasmapto()		check if a mapping exists
 	mapcheck()		check if a matching mapping exists
 	maparg()		get rhs of a mapping