Weekly report creation

The COVID-19 Forecast Hub has developed a weekly report that summarizes aspects of the most recent forecast. The code to generate the report is public and the reports are listed on the Hub website. The process for updating the weekly report is as follows:

1. Confirm that the COVIDhub-ensemble model has been run for the week, uploaded to GitHub, and added to Zoltar.
2. Navigate to the code/reports/ directory of the covid19-forecast-hub repo in RStudio and run the following command: rmarkdown::render(input="weekly-report.Rmd", output_file=paste0(Sys.Date(), "-weekly-report.html")).
3. Commit the resulting HTML file and either push to master or submit a PR to add it to the main covid19-forecast-hub repository.
4. Copy the resulting HTML file to covid19-forecast-hub-web/reports/ directory.
5. Add a link to the HTML file on the reports index page.
6. Run the web deployment script by following these instructions.