[New] (JapanData) the number of vaccinated persons in Japan

[lisphilar]

Summary of this new feature

I added two variables to Japan dataset. https://github.com/lisphilar/covid19-sir/tree/master/data

• Vaccinated_1st: the number of vaccinated persons for the first time on the date
• Vaccinated_2nd: the number of vaccinated persons with the second dose on the date

Data source (in Japanese): https://www.mhlw.go.jp/stf/seisakunitsuite/bunya/vaccine_sesshujisseki.html

Note: These variable names may be changed in the future.

These variables will be included in JapanData.cleaned().

[lisphilar]

Variables of JapanData.cleand() will includes

• Vaccinations: the number of vaccinations, cumsum of Vaccinated_1st + cumsum of Vaccinated_2nd
• Vaccinated_once: the number of people who have recieved at least one dose, cumsum of Vaccinated_1st
• Vaccinated_full: the number of people who has been fully vaccinated, cumsum of Vaccinated_1st

This is because VaccineData.cleaned() will have these variables as discussed in #609.