Add 'inbounds' display range to geom_football

[nguyenank]

Add a default display range for football geoms that only displays what's in play.

[rossdrucker]

I've gone ahead and tried to implement this for all surfaces, not just football. The football-specific result looks like this:

geom_football(
  "nfl",
  "in bounds only"
  color_updates = list(
    "sideline" = "#ff552e",
    "end_line" = "#13294b"
  )
)

Note: Colors of sideline and end line changed to make them stand out from background of plot

Is that what you had in mind?

[nguyenank]

Yep; that's pretty much exactly what I was thinking!

[rossdrucker]

Closed via #19