Add types for web3-eth-abi

[LogvinovLeon]

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[typescript-bot]

@LogvinovLeon Thank you for submitting this PR!

Because this is a new definition, a DefinitelyTyped maintainer will be reviewing this PR in the next few days once the Travis CI build passes.

In the meantime, if the build fails or a merge conflict occurs, I'll let you know. Have a nice day!

[levino]

I am not sure that this is the right approach. web3-eth-abi is a more or less a subpackage of web3. So maybe it makes more sense to type the whole web3-* family in one go. Also web3 provides its own, currently broken type definitions. In principle this means that there generally is some kind of "intend" to also provide typings to the subpackages. Either way I think all definitions for the web3 submodules should be either maintained here or over at the web3 repo.

I think this PR was accepted without reviewing in depth and without having a proper plan for the matter.