[mapping] Update docs

Author: clydebarrow

components/mapping.rst

@@ -1,7 +1,8 @@
 Mapping Component
 -----------------
 
-The `mapping` component allows you to create a map or dictionary that allows a one-to-one translation from keys to values. This enables e.g. mapping a string to a number or vice versa, or mapping a string such as a weather condition to an image.
+The `mapping` component allows you to create a map or dictionary that allows a one-to-one translation from keys to
+values. This enables e.g. mapping a string to a number or vice versa, or mapping a string such as a weather condition to an image.
 
 .. code-block:: yaml
 
@@ -32,6 +33,7 @@ Configuration variables:
 - **to** (**Required**, string): The type of values in the map. May be one of ``string`` or ``int`` or a class specifier as discussed below.
 - **entries** (**Required**, dict): A list of key-value pairs that define the mapping. The keys must be of the type specified in the ``from`` field, and the values must be of the type specified in the ``to`` field.
 
+
 Mapping to a class
 ##################
 
@@ -44,7 +46,11 @@ You can also map to a class. This is useful when you want to map to a more compl
 Using a mapping
 ###############
 
-A mapping defined in this component can be used in lambdas in other components. The mapping can be accessed using the ``id`` function, and the value can be looked up using the ``[]`` operator as per the above example.
+A mapping defined in this component can be used in lambdas in other components. The mapping can be accessed using
+the ``id`` function, and the value can be looked up using the ``[]`` operator as per the above example, or the ``get`` function.
+A map may be updated at run time using a lambda call, e.g. ``map["key"] = value`` or ``map.set("key", value)``.
+
+Maps are stored in RAM, but will use PSRAM if available.
 
 A more complex example follows:
 
@@ -73,6 +79,8 @@ A more complex example follows:
         hex: 00FF00
       - id: blue
         hex: 0000FF
+      - id: magenta
+        hex: FFFF00
 
     font:
       - file: gfonts://Roboto
@@ -84,10 +92,15 @@ A more complex example follows:
       - platform: ...
         # update the display drawing random text in random colors
         lambda: |-
-          auto color = color_map[random_uint32() % 3];
+          auto color = color_map.get(random_uint32() % 3]); # Uses get() to index the color_map
           it.printf(100, 100, id(roboto20), color, id(string_map)[random_uint32() % 3].c_str(), Color(0));
 
 
+    on_...:
+      then:
+        - lambda: |-
+              id(color_map)[2] = Color::random_color();
+
 See Also
 --------