Addition of codecov to check code coverage

[agbilotia1998]

Is your feature request related to a problem? Please describe.
Since the project has few unit tests added, codecov could be added to check code coverage and improve the test suite.

Describe the solution you'd like
Addition of codecov.

[agbilotia1998]

@michalmikolajczyk would you be auditing this issue through gitcoin?

[michalmikolajczyk]

@agbilotia1998 probably, but we have planned work for a few months to come. We added this task to the next phase of our backlog, we will revisit in a few weeks time. Just as with the other task ;)