Move leading commas to end of previous line

[rjake]

Similar to #402 I would like for arguments on a new row that begin with a comma to move up to the previous line

When I use this code:

x <-
    "mpg %>%
    summarise(avg_cty = mean(cty)
              , avg_hwy = mean(hwy)
              , n = n()
              , n_class = n_distinct(class))"

style_text(x)

I get this result:

[lorenzwalthert]

Thanks @rjake. Indeed, #402 was only solved partially. Now I hope with #479 we can cover it fully.