fix(shape/AreaClosed): set y0 when it equals zero

[williaster]

🐛 Bug Fix

Fixes a small issue I noticed when answering #954 , we don't set y0 when it is 0 because of the truthy/falsy logic. A work around for now is to set y0={() => 0}

@kristw @hshoff
cc @puchm

[coveralls]

Pull Request Test Coverage Report for Build 395151044

Warning: This coverage report may be inaccurate.

This pull request's base commit is no longer the HEAD commit of its target branch. This means it includes changes from outside the original pull request, including, potentially, unrelated coverage changes.

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Details

• 1 of 2 (50.0%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 59.864%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
packages/visx-shape/src/shapes/AreaClosed.tsx	1	2	50.0%

Totals
Change from base Build 395106080:	0.0%
Covered Lines:	1634
Relevant Lines:	2571

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💛 - Coveralls