Restore action has no icon

[jancborchardt]

The restore action does not seem to have an icon – we should simply use the ➕ icon-add for it.

[nickvergessen]

also the green one, or a monochrome one, so there is a difference?

[jancborchardt]

Actually even better would be icon-history: https://github.com/nextcloud/server/blob/master/core/img/actions/history.svg

That’s monochrome, and it’s also symmetric to the restore action from deleted files.