Added missing sections: GuiState, Interactable

[vifgaming1]

There was just nothing in those 2 sections.

Changes

GuiObject.GuiState and GuiObject.Interactable now have short summaries and long descriptions of how they work.

Checks

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[github-actions]

Hi @vifgaming1, thanks so much for helping improve the Roblox creator documentation! Our technical writing team will review your pull request soon. In the meantime, please ensure you've read through the README.md, contribution guidelines, and style recommendations.