reproduce figures in {cfr} paper comparing observed vs predicted

[avallecam]

from translation review by @Karim-Mane

use the horizontal lines as in slides but with code in echo=FALSE

in

tutorials-middle/episodes/severity-static.Rmd

Lines 543 to 555 in a7cd432

	:::::::::::::::::::::::::::::::::: spoiler
	### Case study: SARS outbreak, Hong Kong, 2003
	Figures A and B show the cumulative numbers of cases and deaths of SARS, and Figure C shows the observed (biased) CFR estimates as a function of time, i.e. the cumulative number of deaths over cases at time $t$. Due to the delay from the onset of symptoms to death, the biased estimate of CFR at time $t$ underestimates the realised CFR at the end of an outbreak (i.e. 302/1755 = 17.2 %).
	)](fig/cfr-pone.0006852.g003-fig_abc.png)
	Nevertheless, even by only using the observed data for the period March 19 to April 2, `cfr_static()` can yield an appropriate prediction (Figure D), e.g. the delay-adjusted CFR at March 27 is 18.1 % (95% CI: 10.5, 28.1). An overestimation is seen in the very early stages of the epidemic, but the 95% confidence limits in the later stages include the realised CFR (i.e. 17.2 %).
	)](fig/cfr-pone.0006852.g003-fig_d.png)
	::::::::::::::::::::::::::::::::::