[MNT] Add codecov

[surchs]

Changes proposed in this pull request:

• Let's take a look at codecov for our coverage needs

Checklist

• [ ] PR has an interpretable title with a prefix ([ENH], [FIX], [REF], [TST], [CI], [MNT], [INF], [MODEL], [DOC]) _(see https://neurobagel.org/contributing/pull_requests for more info)_
• [ ] PR links to GitHub issue with mention Closes #XXXX
• [ ] Tests pass
• [ ] Checks pass

For new features:

• [ ] Tests have been added

For bug fixes:

• [ ] There is at least one test that would fail under the original bug conditions.

[coveralls]

Pull Request Test Coverage Report for Build 7176998385

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 98.322%

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Totals
Change from base Build 7176871175:	0.0%
Covered Lines:	293
Relevant Lines:	298

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💛 - Coveralls

[codecov[bot]]

Welcome to Codecov :tada:

Once merged to your default branch, Codecov will compare your coverage reports and display the results in this comment.

Thanks for integrating Codecov - We've got you covered :open_umbrella:

[surchs]

We're closing this PR in favour of doing the codecov setup in bagel-cli for the first time