Mentioned age restriction for monetizing plugins.

[snoopythe3-from-scratch]

Changes

Mentioned age restriction for monetizing plugins.

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[github-actions]

Hi @snoopythe3-from-scratch, 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.