Feature: allow storage-class in Human-Readable ABI

[ricmoo]

The Human-Readable ABI currently does not allow storage-class in a fragment, which may mean the signature cannot be directly copied from the Solidity.

For example, this should work fine:

const abi = [
    "function foo(string memory bar)"
];

However, the memory and storage keywords are not supported by the parser. It is a simple state transition required when reading a space, to check in the same way the keyword indexed is processed, which can discard the name and revert the parser state back to allowName.

[ricmoo]

Added! :)