load static method
Load the store for the project at root. A missing file yields an
empty store (not an error). Throws FormatException if the file is
present but malformed.
Implementation
static StateStore load(String root) {
final file = File(p.join(root, '.dialect', 'state.json'));
if (!file.existsSync()) return StateStore();
return parse(file.readAsStringSync());
}