Updates from review
Changes from review
Nested example
Update docs/types/mapping-types.rst
Co-Authored-By: chriseth <chris@ethereum.org>
Changes from review
Bring example inline with ERC20
Clarify what maps where
Use OZ contract example
Update docs/types/mapping-types.rst
Co-Authored-By: chriseth <chris@ethereum.org>
update code example