Allow initial parameter values to be passed to dixoncoles

[Torvaney]

Might be useful/faster when refitting values over time?

Something like:

fit <- dixoncoles_ext(hgoal ~ off(home) + def(away) + hfa + 0,
                      agoal ~ off(home) + def(home) + 0,
                      weight = ~ some_weighting(column_name)
                      data = games,
                      init = rep(0, 20))

• refitting of the model with purrr::accumulate

[Torvaney]

Closed by 5fe9f5a