Get spns of a pgn? about canparse HOT 1 OPEN

Hey, thanks for the interest and good idea! I eventually wanted to get to #17 to speed up SPN lookups, but that would probably entail breaking the internal PGN/SPN model. That said, do you see needing any other functionality beyond iterating the SPN map? Otherwise, I like the idea of exposing an API to do this, maybe something like:

impl PgnDefinition {
    ...
    pub fn spns() -> impl Iterator<Item = (&String, &SpnDefinition)> { ... }

which is basically just a proxy for pgnDef.spns.iter(), but should be pretty semver-resilient, I think.

from canparse.