Update ethereum schemas to fit the official response types

[phoenix-web3]

• I have read the Contributing file of the documentation.
• I have searched the issues (including closed ones) and believe that this is not a duplicate.
• I am willing to lend a hand to help implement this feature.

Feature Request

Feature Description

While searching for the data type of "uncles" in issue #120 I came across the following website that specifies exactly the data type in the response of each of the ethereum RPC methods.

This specification covers use cases that can occur when calling an ethereum RPC method.

I suggest copying, as far as possible, the schemas for ethereum API calls.

It also could be a good idea to copy the patterns

Use Case(s)