Use the `yaml` package to write .yml

[athowes]

• Could saves rewriting same code for different iso3 parameters
• Write yaml in R, then call 'yaml::as.yamlandwriteLines`
• See: https://github.com/mrc-ide/mics-datasets/blob/master/src/mics_rds/script.R#L100-L110 or https://github.com/mrc-ide/mics-datasets/blob/master/src/download_mics_datasets/script.R#L75-L78

[athowes]

Not going to do this, but worth remembering for future perhaps.