An addon for Dexie.js that keeps track of opened connections
When a new Dexie is instanciated ie new Dexie(dbName, { addons: [ DexieOpenedDatabasesAddon ] }).open(), this instance is kept as Dexie.openedDatabases, in a Map with the database name as key.
When the connection is closed ie db.close(), its instance is removed from the Dexie.openedDatabases Map.