docs: update Virtualizer types, fix measureElement method reference, and add optional modifiers

[wo-o29]

🎯 Changes

• Corrected types in the Virtualizer documentation to match the actual implementation found in VirtualizerOptions, Virtualizer.
• Fixed the incorrect reference of virtualItem.measureElement to the correct Virtualizer.measureElement method.
• Added missing optional (?) modifiers for optional options to maintain consistency and improve clarity for users.
• fix typo occations ➔ occasions

✅ Checklist

• I have followed the steps listed in the Contributing guide.
• I have tested and linted this code locally.
• I have generated a changeset for this PR, or this PR should not release a new version.

[changeset-bot]

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Latest commit: 62e75a7

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