Following nearly all other subdirectories in Emacs's etc/, add a
README explaining what the files are and what license they are under.
I did not add these files, but I have verified that
- etc/csl/chicago-author-date.csl is identical to
9821a884d2cbf919a064426999b05aa78e98da8d:chicago-author-date.csl
from https://github.com/citation-style-language/styles
- etc/csl/locales-en-US.xml is identical to
a2b76b20ee120979ec66cfdcfa798b36fc5a7f0b:locales-en-US.xml from
https://github.com/citation-style-language/locales
Kyle Meyer