add localhost to unsafeHttpWhitelist

[quisido]

What's the problem this PR addresses?

My development environment uses an internal NPM registry proxied via a port on localhost. Like most localhosts, it does not support https. As a result, my .yarnrc.yml file is in a constant state of error: String does not match the pattern of "[-a-zA-Z0-9@:%._\+~#=]{1,256}\.[a-zA-Z0-9()]{1,6}\b([-a-zA-Z0-9()@:%_\+.~#?&//=]*)".yaml-schema: Array of hostname glob patterns for which using the HTTP protocol is allowed.

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How did you fix it?
I added localhost to the allowed pattern.

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Checklist

• I have read the Contributing Guide.
• I have set the packages that need to be released for my changes to be effective.
• I will check that all automated PR checks pass before the PR gets reviewed.