plot_marker_sequence: Plot the sequence of marker values
In SDAMcIntyre/countenance: Read, process and analyse facial EMG data

Create a ggplot object, plotting the sequence of transitions found in a marker channel, and highlighting unexpected values in red.

plot_marker_sequence(
  femg_data,
  marker_channel,
  unexpected_channel = "unexpected",
  time_channel = "time_sec"
)

`femg_data`	data frame or tibble
`marker_channel`	the name of the column in femg_data that corresponds to the marker channel
`unexpected_channel`	the name of the column in femg_data that is a boolean indicating if the channel was unexpected
`time_channel`	the name of the column in femg_data that gives the time in seconds