Make the document field toolbar wrap

[JedWatson]

This change make the toolbar wrap when the viewport is small enough.

@mitchellhamilton I'm not sure why it was a grid in the first place, this doesn't seem to have changed anything else... I also removed the spacing, we could add it back but it looks fine and is slightly less likely to wrap this way

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🦋 Changeset detected

Latest commit: e37c77b

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
@keystone-next/fields-document	Patch

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[gautamsi]

I also noticed that the document field on maximizing does not cover the full height of page. should that be fixed too?