Allow gg_season to remove minor breaks from the plot

[sillasgonzaga]

This is a plot produced with gg_season():

It feels to me that the minor breaks between each month are quite unnecessary and we could have a parameter in the function to remove them (or even remove them without even asking the user)

[mitchelloharawild]

Good idea, for plots where there is a 1:1 mapping between time points and breaks minor breaks are not needed. I'd be happy to accept a PR for this.