Prevent duplicative frame names

[sawyerclick]

Describe the bug

If two or more frames share a name, only one is produced, causing an unexpected issue. While identically named frames are a mistake, we should prevent that on our end. Ditto for single frames

Reproduction

1. Create a figma2html copy https://www.figma.com/community/plugin/1109185297790825980/figma2html.
2. name two artboards the same
3. export and count the number of assets

Logs

No response

System Info

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Severity

annoyance

Code of Conduct

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