Add 'Copy' button or action next to/inside the published link

### What
Once a note is published and the URL is generated, it would be nice to have a faster way of copying the URL than selecting text and Cmd+C.

### Why
Do things faster. In different forms present in iOS, Electron and Android.

### How
Either a separate button, or a click inside the field with URL to copy to the clipboard.

Start at the macOS UI shown after a note is published, where the generated URL is displayed. Determine the existing published-link entry point and how clipboard actions are handled in the app. Done means users can copy the generated URL through a visible button or an action on the URL field.

Written by the indexing model from the issue text.