It doesn't work, you can't turn a MWMagicLinkNode into text by
clearing its styling. (You can still do that by clicking 'Edit',
'Convert to simple link', 'Clear styling'.)
`clearable = true` was being inherited from ve.ui.LinkContextItem.
Change-Id: Ib40e952554966fb74b3e72662a6e1e44ad748a57
Implement a special node type, context item, and inspector for
ISBN/PMID/RFC magic links. Add buttons to the link inspectors
to convert back and forth between "simple" links, and magic links.
Depends on I5d000d8b63dafdfe0a2753069d3f0ac5b03b8829 in Parsoid
for clean round-tripping of localized ISBN magic links.
Bug: T63558
Change-Id: Id5b7a2ae3c80b0e5eed598f0bd024d3e94f7e9aa
