fix: add types for selector playground

[panzarino]

Adds missing types for selector playground

Note: looks a little different than our other dom signatures that accept either a jquery or html element - selector playground getSelector actually only works with jquery element

• Have tests been added/updated?
• Has the original issue or this PR been tagged with a release in ZenHub?
• Has a PR for user-facing changes been opened in cypress-documentation?
• Have API changes been updated in the type definitions?
• Have new configuration options been added to the cypress.schema.json?

[cypress-bot]

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[cypress]

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Test summary

9494 • 0 • 111 • 3 • 0

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Run details

Project	cypress
Status	Passed
Commit	3b4bca5
Started	Apr 13, 2021 7:45 PM
Ended	Apr 13, 2021 8:00 PM
Duration	14:33 💡
OS	Linux Debian - 10.8
Browser	Multiple

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[cypress-bot]

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