Show the file URL on an asset's edit page

[redburn]

When you open an asset's edit page, its public URL isn't shown anywhere. For images, the preview gives you a hint, but for documents (PDF, docx, etc) the View button just downloads the file and you never see the address. The only way to copy it is to go back to the asset index, select the file and use Copy URL from the actions menu or right-click the globe icon in the Link column.

Editors sometimes need a document's link to paste into an email or another site. Seeing the URL on the edit page, with a way to copy it, would save that detour to the asset index page.