ggplot2 3.3.2

This is a small release focusing on fixing regressions introduced in 3.3.1.

• Added an outside option to annotation_logticks() that places tick marks
  outside of the plot bounds. (#3783, @kbodwin)

• annotation_raster() adds support for native rasters. For large rasters,
  native rasters render significantly faster than arrays (@kent37, #3388)

• Facet strips now have dedicated position-dependent theme elements
  (strip.text.x.top, strip.text.x.bottom, strip.text.y.left,
  strip.text.y.right) that inherit from strip.text.x and strip.text.y,
  respectively. As a consequence, some theme stylings now need to be applied to
  the position-dependent elements rather than to the parent elements. This
  change was already introduced in ggplot2 3.3.0 but not listed in the
  changelog. (@thomasp85, #3683)

• Facets now handle layers containing no data (@yutannihilation, #3853).

• A newly added geom geom_density_2d_filled() and associated stat
  stat_density_2d_filled() can draw filled density contours
  (@clauswilke, #3846).

• A newly added geom_function() is now recommended to use in conjunction
  with/instead of stat_function(). In addition, stat_function() now
  works with transformed y axes, e.g. scale_y_log10(), and in plots
  containing no other data or layers (@clauswilke, #3611, #3905, #3983).

• Fixed a bug in geom_sf() that caused problems with legend-type
  autodetection (@clauswilke, #3963).

• Support graphics devices that use the file argument instead of fileneame
  in ggsave() (@bwiernik, #3810)

• Default discrete color scales are now configurable through the options() of
  ggplot2.discrete.colour and ggplot2.discrete.fill. When set to a character
  vector of colour codes (or list of character vectors) with sufficient length,
  these colours are used for the default scale. See help(scale_colour_discrete)
  for more details and examples (@cpsievert, #3833).

• Default continuous colour scales (i.e., the options()
ggplot2.continuous.colour and ggplot2.continuous.fill, which inform the
  type argument of scale_fill_continuous() and scale_colour_continuous())
  now accept a function, which allows more control over these default
  continuous_scale()s (@cpsievert, #3827).

• A bug was fixed in stat_contour() when calculating breaks based on
  the bins argument (@clauswilke, #3879, #4004).

• Data columns can now contain Vector S4 objects, which are widely used in the
  Bioconductor project. (@teunbrand, #3837)