Work in progress: It's not yet possible to paste from the pane.

The pane can be switched to and from and displays the strings recently
added to the clipboard.

ClipboardHistoryService listens for change to the system clipboard and
keep the history in memory.
This data is not persisted to the storage.

The maximum size limits the amount of user data stored in memory but
also gives a sense to the user that the history is not persisted and can
be forgotten as soon as the app stops.

Allow recent clips to be pinned. Pinned clips are put a different place
and are persistent.

The pane is split in two columns, the clipboard history and the pinned
clips.

Pinned clips are stored in a new preference file.

Improved pinning layout

clipboard: Remove history entry after pinning

Slightly improves privacy. Entries older than that are not useful in the
intended use case.

Put the recently copied text at the top and the pinned text at the
bottom.
This should remain intuitive as the recent history should stay small.

The feature is off by default for privacy reasons. The checkbox state is
persisted in the configuration.

The history is immediately cleared when it's disabled. The content of
the system clipboard is visible when the history is enabled.

The paste button send the content of the pinned clip to the editor the
same way as a string key.

Prevent accidentally deleting a saved clipboard.

To make it less ambiguous with the clipboard key icon.

These don't have any effect.