Add button to download excel file of dashboard pangolin weekly table

[moedarrah]

After discussing the issue with @LordRust, the download button should have two options: per week, and per date. Also, we will have the year next to week number

[moedarrah]

Right now the endpoint has only per_date. we need to add a new array with the per_week data. @Fattigman example: { "per_date": [ { "date": "string", "pango_count": 0, "pangolin": "string" } ], "per_week": [ { "date": "string", // week number with the year "pango_count": 0, "pangolin": "string" } ], "general_stats": { "passed_qc_samples": 0, "unique_pangos": 0, "unique_mutations": 0 }, "selection_criterions": [ "string" ] }