Places minor breaks between major breaks.
Examples
m <- extended_breaks()(c(1, 10))
regular_minor_breaks()(m, c(1, 10), n = 2)
#> [1] 0.00 1.25 2.50 3.75 5.00 6.25 7.50 8.75 10.00
n <- extended_breaks()(c(0, -9))
regular_minor_breaks(reverse = TRUE)(n, c(0, -9), n = 2)
#> [1] -10.00 -8.75 -7.50 -6.25 -5.00 -3.75 -2.50 -1.25 0.00