🚀 Consider making README.md mention that color settings in .gitconfig can override delta's colors

[derat]

New user here -- thanks for making delta!

I just spent an embarrassingly long time debugging why delta was displaying added and removed lines with my terminal's default background color instead of the configured background colors. Oddly, I only saw this problem when I ran e.g. git show; delta used the configured background colors when I ran e.g. git show | delta instead.

I finally figured out that it was due to a previously-added color "diff" section in my .gitconfig file:

[color "diff"]
  meta = brightcyan
  old = brightred
  new = brightgreen

It'd helpful to make the "Get Started" section of README.md mention that settings like these can override delta's behavior to save other people some time. :-)