update docs for bool to match code (#911)

* update docs for bool to match code

* add changelog

changes/911-trim21.md

@@ -0,0 +1 @@
+update docs for bool missing valid value.

docs/usage/types.md

@@ -239,7 +239,7 @@ A standard `bool` field will raise a `ValidationError` if the value is not one o
 * A valid boolean (i.e. `True` or `False`),
 * The integers `0` or `1`,
 * a `str` which when converted to lower case is one of
-  `'off', 'f', 'false', 'n', 'no', '1', 'on', 't', 'true', 'y', 'yes'`
+  `'0', 'off', 'f', 'false', 'n', 'no', '1', 'on', 't', 'true', 'y', 'yes'`
 * a `bytes` which is valid (per the previous rule) when decoded to `str`
 
 !!! note