Add country Peru (PE)

Lists of the usual public holidays can be found in

- https://en.wikipedia.org/wiki/Public_holidays_in_Peru
- https://www.officeholidays.com/countries/peru/2020
- https://publicholidays.pe/2020-dates/

Also, this website lists all the extra holidays that could've been decreed on a given year:

- https://www.timeanddate.com/holidays/peru/

Start by reviewing existing country holiday entries in the repository and compare their structure with the Peru sources listed in the issue. Add Peru (PE) with its usual public holidays and account for extra holidays where the project supports them; done means Peru is represented consistently with the other countries.

Written by the indexing model from the issue text.