fix: type definition. rowHeaders of IGridOptions of index.d.ts #321

[BillionaireDY]

fix: wrong type definition (ref #321)

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Description

The rowHeaders of IGridOptions of index.d.ts is defined differently from the document.
ref) #321

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Thank you for your contribution to TOAST UI product. 🎉 😘 ✨

[jung-han]

Can one of the admins verify this patch?

[jung-han]

Thanks for your contribution. We are going to apply this PR in the v3.8.0. 🤟

[jung-han]

ok to test