Update documentation for cases to include re-infections starting 2021-11-15

[krivard]

From Roni on 2021-11-15:

Important: I heard on NPR's this morning that COVID re-infection cases (a confirmed COVID infection more than 90 days after a previously confirmed COVID infection), which have not been reported/counted in the past, will be reported/counted going forward. And I just got Allegheny County's daily email which said:

• Note: Effective today, state databases have added historical reinfection data for positive cases that occurred more than 90 days apart, boosting overall cases since March 14, 2020 by an additional 1,302 cases. Moving forward, daily case totals will include new cases plus reinfections.

We'll need to update:

• https://github.com/cmu-delphi/delphi-epidata/blob/dev/docs/api/covidcast-signals/jhu-csse.md
• https://github.com/cmu-delphi/delphi-epidata/blob/dev/docs/api/covidcast-signals/usa-facts.md
• the meta sheet
• the description doc for the website
• possibly the anomalies sheet if there's a big spike on the 15th to make note of.

Do not update the indicator-combination documentation; we've been meaning to discontinue it and this is as good an excuse as any.