Updating battery descriptions

[victorventuri]

Changed 'manufacturer' and 'design' to be optional, so that loading experimental lab data without these fields is possible. Fixes #70

@WardLT I am not familiar with pydantic, can you double check for me?

[coveralls]

Pull Request Test Coverage Report for Build 9370489088

Details

• 2 of 2 (100.0%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 83.495%

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Totals
Change from base Build 9099801032:	0.0%
Covered Lines:	774
Relevant Lines:	927

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💛 - Coveralls

[WardLT]

Nicely done, @victorventuri ! You did do the optional fields correctly. Check out this for reference: https://docs.pydantic.dev/latest/migration/#required-optional-and-nullable-fields