WARNING: It's a WIP. If you wish to you can review the PR but it's not finished yet.

Summary of Changes

Adds support for WebSockets that will be part of 4.0 release.

DefaultWeb3SocketClient was added and is based on the native URLSessionWebSocketTask. It's wrapped in #if !os(Linux) ... #endif so we can add a separate instance of DefaultWeb3SocketClient for Linux based on some other library that supports Linux.

Issues that are left to resolve/add:

• Linux support;
• Location of Keystore. At the moment it's in the Web3Provider. This branch is based on New WebsocketProvider and Subscriptions implementation #446 and that PR had moved the attachedKeystore to the web3 class;
• Tests;
• The rest of compile errors.

Test Data or Screenshots

empty

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