Get all needed styles into the Next.js app

[MichaelAllenWarner]

Some style-rules for block-markup in the Plugin repo don't have counterparts in the Next.js app (or in the framework). For example, this rule:

.has-white-color {
    color: var(--wp--preset--color--white) !important;
}

Not sure what the best approach is yet, but we'll have to account for these styles one way or another.

[MichaelAllenWarner]

Renamed this issue to be as broad as possible for now. Once we know more about the specifics, maybe we can break this up into a few more specific issues.