get preferences directly instead of parsing divvun-checker -p

[unhammer]

@bbqsrc

divvun-api/src/language/grammar.rs

Line 282 in 4d655aa

pub fn list_preferences(data_file_path: &str) -> Result<BTreeMap<String, String>, Error> {

divvun-checker -p is just a "human-readable" summary of preferences, was never meant for computer consumption. Can divvun-api read the errors.xml directly? Or divvun-checker could just output the xml if you want to avoid doing the unzip.

cf. divvun/libdivvun#80