Improve dist_transformed method

[mitchelloharawild]

library(distributional)
fabletools::inv_box_cox(dist_normal(), 0.1)
#> Warning in mapply(get(op), x = x, y = y, SIMPLIFY = FALSE): Incompatible methods
#> ("Ops.dist_transformed", "*.vctrs_vctr") for "*"
#> Error in .Primitive("*")(x = dots[[1L]][[1L]], y = dots[[2L]][[1L]]): non-numeric argument to binary operator

^{Created on 2020-04-14 by the reprex package (v0.3.0)}