chore: Add a coveralls yaml file

[mlms13]

Honestly I have no memory of how this CI step is supposed to work, but it seems like it's currently failing on the coverage step, and some people on the internet suggested it might work to add a .coveralls.yml file. 🤞

[coveralls]

Pull Request Test Coverage Report for Build 183

• 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 99.781%

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Totals
Change from base Build 181:	0.0%
Covered Lines:	847
Relevant Lines:	849

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💛 - Coveralls