Feature: import/export of local storage as json #8
Description
local storage persists in the browser but it can be cleared easily. this feature aims at helping the user to backup their storage to resume where they left off.
- import option with version check to ensure data can be used
- warn user before import that all existing storage will be deleted
- export option to download as json file
- consider a dialog that allows the user to name the export, giving a default value of the date+time
- version control the object exported so that importing can match versions
- consider an upgrade path with version numbers, this might not be possible