fix: prevObject types

[atarek12]

• Closes Typescript error while using Cypress.Command.add(): Property 'selector' does not exist on type 'JQuery<HTMLElement>' #20376

User facing changelog

Fix Cypress.Command.add() TypeScript types. Fixes #20376

• Infer the subject type to be an element while using prevSubject: true option
• Adding property selector to the subject while using prevSubject: true | "element" option

Additional details

This change fixes typescript errors while using the Cypress.Command.add() with { prevSubject: true } or { prevSubject: "element" }

How has the user experience changed?

No typescript error while trying to access the selector.

Cypress.Commands.add("newCommand", { prevSubject: "element" }, (element) => {
  element.selector // no typescript error
});

PR Tasks

• Have tests been added/updated?
• Has the original issue (or this PR, if no issue exists) been tagged with a release in ZenHub? (user-facing changes only)
• 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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[atarek12]

@flotwig here is the new PR against the latest changes in the develop branch as you requested here

[cypress-bot]

Released in 9.6.0.

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