exmort 0.1.0

• First release: the WHO WPRO All-Cause and Excess Mortality Calculator packaged as an R package.
• run_app() launches the bundled Shiny application from a temporary directory.
• Includes seven baseline models (historical average, negative binomial, quasi-Poisson, zero-inflated Poisson, ARIMA/SARIMA, GAM spline and the Karlinsky–Kobak model), event annotation, best-fit AIC comparison, and HTML / Word / PDF report generation.
• Application code is sourced into a private environment instead of the global environment, and the app no longer leaves options(digits) or the LC_TIME locale changed after a session ends.
• Adds a testthat suite covering the ISO year-week date helpers, the model date index and the upload validators.