Package font defines an interface for font faces.
Other packages provide font face implementations. For example, a
truetype package (not part of this CL) would provide one based on .ttf
font files.
This CL also introduces the golang.org/x/exp/shiny/font/plan9font
package, a concrete implementation of the font.Face interface for the
Plan 9 bitmap font format.
Change-Id: Iead8914caaa58c7562b18a86b45002ae47486903
Reviewed-on: https://go-review.googlesource.com/13463
Reviewed-by: Rob Pike <r@golang.org>
