Add code owners file

[Floppy]

@gjtorikian is this list right do you think?

[codecov-io]

Codecov Report

Merging #455 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #455   +/-   ##
=======================================
  Coverage   98.52%   98.52%           
=======================================
  Files          27       27           
  Lines        1762     1762           
=======================================
  Hits         1736     1736           
  Misses         26       26

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[gjtorikian]

Thanks!