Add expected value for requiredIf

[jettcalleja]

Proposed changes

This is inspired to laravel's requiredIf functionality wherein the field under validation must be present and not empty if the anotherfield field is equal to any value.

Types of changes

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• [ ] Bugfix (non-breaking change which fixes an issue)
• [x] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to not work as expected)

Checklist

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• [x] I have read the CONTRIBUTING doc
• [x] Lint and unit tests pass locally with my changes
• [x] I have added tests that prove my fix is effective or that my feature works.
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[thetutlage]

Yup, looks like a great addition

[thetutlage]

Thanks 😄