doc: Confirm that map works recursively

The `map` function on the HP48 is supposed to be recursive.
Document that fact.

Related to #1649

Signed-off-by: Christophe de Dinechin <christophe@dinechin.org>

Author: c3d

doc/commands/lists.md

@@ -46,6 +46,14 @@ first level of the stack should take one argument and return a single value.
 
 `{ A B ... }` `F` ▶ `{ F(A) F(B) ... }`
 
+The operation applies recursively to inner lists.
+
+```rpl
+{ 1 2 { 3 4 } } « →STR » MAP
+@ Expecting { "1" "2" { "3" "4" } }
+
+```
+
 ## Reduce
 
 Apply a cumulative pairwise operation on all elements in a list or array.

help/db48x.md

@@ -12559,6 +12559,14 @@ first level of the stack should take one argument and return a single value.
 
 `{ A B ... }` `F` ▶ `{ F(A) F(B) ... }`
 
+The operation applies recursively to inner lists.
+
+```rpl
+{ 1 2 { 3 4 } } « →STR » MAP
+@ Expecting { "1" "2" { "3" "4" } }
+
+```
+
 ## Reduce
 
 Apply a cumulative pairwise operation on all elements in a list or array.

help/db50x.md

@@ -12567,6 +12567,14 @@ first level of the stack should take one argument and return a single value.
 
 `{ A B ... }` `F` ▶ `{ F(A) F(B) ... }`
 
+The operation applies recursively to inner lists.
+
+```rpl
+{ 1 2 { 3 4 } } « →STR » MAP
+@ Expecting { "1" "2" { "3" "4" } }
+
+```
+
 ## Reduce
 
 Apply a cumulative pairwise operation on all elements in a list or array.