feat(valid-v-for): add allowEmptyAlias option

[waynzh]

resolve #2733.
Add an option to support this type of valid syntax.

[changeset-bot]

🦋 Changeset detected

Latest commit: a0079c7

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
eslint-plugin-vue	Minor

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[Copilot]

Pull request overview

This PR adds a new allowEmptyAlias option to the vue/valid-v-for rule, addressing issue #2733. The feature allows developers to use empty aliases in v-for expressions, which is useful when iterating over objects where only certain parameters (like keys) are needed without the value.

Changes:

• Added allowEmptyAlias boolean option to valid-v-for rule (defaults to false for backward compatibility)
• Updated rule logic to conditionally allow null/empty aliases based on the option
• Added test coverage for the new option with both valid and invalid scenarios
• Documented the new option with configuration examples

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 5 comments.

File	Description
lib/rules/valid-v-for.js	Implements the allowEmptyAlias option with schema definition and validation logic
tests/lib/rules/valid-v-for.js	Adds test cases for valid and invalid scenarios with the new option
docs/rules/valid-v-for.md	Documents the new option with configuration examples and code samples
.changeset/giant-cars-open.md	Changeset entry for the minor version bump

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[FloEdelmann]

Can you please change the error message for empty aliases?