maldi_draw_spectrum: Plot a mass spectrum
In benjbuch/summerrmass: Measure and Analyze MALDI Peaks

Draws a mass spectrum using the default method and adds additional points and lines if required.

maldi_draw_spectrum(
  object = NULL,
  xaxt = "s",
  x = NULL,
  y = NULL,
  overlay_color = NA,
  SNR = NaN,
  col = "red"
)

`object`	A `MassSpectrum`.
`xaxt`	A character which specifies the x axis type. See par().
`x, y`	The coordinates of additional points to draw.
`overlay_color`	Color for overlay at 50% transparency.
`SNR`	Level at which the signal-to-noise-ratio should be indicated.
`col`	Color for points and lines.