Add support for generating `preview: true` deployment environment URLs? 🧪

[JamesMGreene]

Tangentially for the 🧪 experimental-alpha-internal-only support that actions/deploy-pages offers for Pages preview deployments per PR 🧪, it would be great if this action could also generate the expected URL for that forthcoming deployment as well earlier in the Actions workflow run so that it could be passed in to the site's build process.

Need to do some more investigation on if the URL that will be generated is consistently predictable. 🤔

[zvailanu98]

#92 (comment)

[mosesgameli]

hi @JamesMGreene any updates on this?

[zvailanu98]

@JamesMGreene