Create bullet graph with reference line
abm_bullet(label, value, reference, roundto = 1, pct = FALSE)
a label for the indicator, shown to the left of the gauge
the value of the indicator, displayed as a horizontal wide line
a reference value displayed as a vertical thin line
number of digits after the decimal point (default = 1)
boolean, set to TRUE if given value is a share (default = FALSE)
a ggplot object