ggfocus 0.81

Added a NEWS.md file to track changes to the package.
Included scale_*_focus() functions for color, alpha and fill aesthetics.
Improved error messages.

ggfocus 1.0.0 (2019-12-23)

ggfocus() is now deprecated. scale_*_focus() should be used.
Focus scales added for size, linetype and shape.
Documentation for all focus scales are now available in a single help file. Use ?scale_focus to view usage and examples.