Add detail about config 'type' attribute to indicate the currently running interpreter.

Author: ntoll

docs/api.md

@@ -56,8 +56,16 @@ from pyscript import config
 
 # It's just a dict.
 print(config.get("files"))
+# This will be either "mpy" or "py" depending on the current interpreter.
+print(config["type"])
 ```
 
+!!! info
+
+    The `config` object will always include a `type` attribute set to either
+    `mpy` or `py`, to indicate which version of Python your code is currently
+    running in.
+
 !!! warning
 
     Changing the `config` dictionary at runtime has no effect on the actual