DAST Site validation - Meta tag

As a user, I would like to use a meta tag on an HTML page on my site to validate that I own the site, so that I don't have upload a separate file or modify my server to include a header.

Requirements

A new validation option added to the validation modal to allow for use of an HTML meta tag with the validation string as the value.

Designs

Implementation Plan

Issue	Description	Type
TBD	Add Meta Tag validation	frontend
TBD	TBD	backend
TBD	TBD	documentation
TBD	TBD	feature flag