Update docs to V3 schema

[owahltinez]

Updating section on 'unique' data set justifications

Update README.md

Update table-by-age.md

update v2 to v3

Update table-by-sex.md

update v2 to v3

Update table-demographics.md

update v2 to v3

Update table-economy.md

update v2 to v3

Update table-emergency-declarations.md

update v2 to v3

Update table-epidemiology.md

update v2 to v3

Update table-geography.md

update v2 to v3

Update table-government-response.md

update v2 to v3

Update table-health.md

update v2 to v3

Update table-hospitalizations.md

update v2 to v3

Update table-index.md

update v2 to v3

Update table-mobility.md

update v2 to v3

Update table-search-trends.md

update v2 to v3

Update table-vaccinations.md

update v2 to v3

Update table-weather.md

update v2 to v3

Update table-worldbank.md

update v2 to v3

Update table-epidemiology.md

Total -> cumulative

Update table-hospitalizations.md

total -> cumulative

Update table-vaccinations.md

total -> cumulative

Update table-vaccinations.md

Changing verbage total -> cumulative

Fix hospitalization and vaccinations fields

Fix table URLs

Fix example notebook

Fix code snippet