post action feedback is the mechanism in which we provide visual feedback
to the user when a post action is clicked, in cases where the action is a
background (hidden to user) for example: copying text to the clipboard
Core uses this to share post links, but other plugins (for example: AI) use
this to share post transcripts via the clipboard.
This adds a proper plugin API to consume this functionality
`addPostMenuButton` can provide a builder that specified a function as the action.
This function will be called with an object that has both the current post and a method for showing feedback.
This commit ports the feature by @chapoi that was
previously a theme component in core.
A new post_menu button, copyLink, is added and used
as the default instead of share.
copyLink, on desktop, will copy the link of the post
to the user's clipboard and show a nice 'lil animation.
On mobile the native share menu will be shown.
If site owners want the old behaviour back, they just
need to change the post_menu site setting to use
the share button instead of copyLink.
Sam
Martin Brennan