Store hash of URLs visited locally to be able to show users in dashboard

[DecentralizedDan]

In the extension dashboard, we need to be able to show users the number of unique URLs they have visited

• This data is stored in the extension (i.e. in a directory in Chrome etc)
• This list must be hashed for privacy
• We must be able to return the number of unique URLs

GanttStart: 2023-09-01 GanttDue: 2023-11-30