arrow_axis: Create miniature arrow to replace axes
In Yutong441/TBdev: Infer a Trophoblast Developmental Trajectory

Create miniature arrow to replace axes

arrow_axis(
  plot_ob,
  length_ratio = 0.05,
  nudge_ratio = 0,
  move_x = 0,
  move_y = 0,
  reverse_x = F,
  reverse_y = F,
  axis_label_sim = F,
  nudge_dimname = 0,
  nudge_ortho = 0,
  aes_param = list(pointsize = 3, font_fam = "Arial", point_fontsize = 6)
)

`length_ratio`	the ratio of the length of the arrow relative to the span of the data
`nudge_ratio`	how much the arrow labels should move away from the arrow tip as a ratio of the length of the arrow
`move_x`	move the arrow axies position by how much to the left, negative value is to the right
`axis_label_sim`	whether to use a simple label i.e. 'dim1', 'dim2'
`nudge_dimname`	if `axis_label_sim` is True, then how much further to the right to move the dim name label
`nudge_ortho`	move the 'dim1', 'dim2' labels etc away from the respective axes orthogonally, i.e. not along the axes
`aes_param`	setting for pointsize, font_fam, point_fontsize, arrow_angle, arrow_length, arrow_length_unit, arrow_type, arrow_thickness, arrow_linejoin
`return`	a list of geoms for the arrow segment and axis labels