Clipboard history (text only)

The intention is to implement just for text to start out but leave as easily extensible for more types

[x] Poll NSPasteboard
[x] Saves a directory per clipboard entry with a metadata file and actual file whenever clipboard is populated
[x] Meta includes number of times copied, last copied at and file extension
[x] Use hash of copied data to deduplicate clipboard items
[x] Observable clipboard history
[ ] Notify JS thread when the clipboard history changes
[ ] Load in clipboard history on app start
[ ] Purge items older than say one day?
[ ] Display clipboard items in react native

ospfranco / sol