Fix: Replaced ethers package with @ethersproject/abi

[RickyRoller]

Description

Updated ethers to 5.x by moving usage to the sub-module @ethersproject/abi In reference to #54

Testing instructions

Types of changes

• Bug fix (non-breaking change which fixes an issue)

Checklist:

• [x] Prefix PR title with [WIP] if necessary.
• [x] Add tests to cover changes as needed.
• [x] Update documentation as needed.
• [x] Add new entries to the relevant CHANGELOG.jsons.

[RickyRoller]

@rhinodavid Do you know who would be the best person to check out this PR?