Document Reusable Editor Components

[youknowriad]

In #2761 we're moving several Editor components to the editor/components folder making them reusable to build custom editor layouts. These components were not meant to be reusable at first, so we need to document their external APIs.

Let's go over these components one by one and:

• Add a README for the component
• Rename the component if necessary (some components need to be prefixed by Post like PostDocumentOutline
• Ensure these components follow our CSS coding guidelines (the classnames)
• If the styles of these components contain any "layout" style making them not easily usable outside the Post Editor context, make sure to refactor these styles out of the component base style.

Here's the list of the components make sure to reference this issue if you work on one of these:

• AutosaveMonitor
• BlockInspector
• BlockToolbar
• DocumentOutline
• Inserter
• MetaBoxes
• PageAttributes
• PostAuthor
• PostComments
• PostExcerpt
• PostFeaturedImage
• PostFormat
• PostLastRevision
• PostPendingStatus
• PostPingbacks
• PostPreviewButton
• PostPublishButton
• PostSavedState
• PostSchedule
• PostSticky
• PostTextEditor
• PostTitle
• PostTaxonomies
• PostTrash
• PostVisibility
• Provider
• UnsavedChangesWarning
• WordCount
• WritingFlow

Thanks for your help

[youknowriad]

I was hoping new contributors will come and document some of these components. I'm going to close this issue as hardly actionable directly. Let's make sure to document the components as we update them.