Add Repo and Org fields to DeployKeyEvent

[IainSteers]

Fixes #2279

[IainSteers]

Hey @gmlewis this should cover the deploy-key event updates.

I've also expanded the marshal test to include the newer fields

[codecov]

Codecov Report

Merging #2280 (e730289) into master (e1c28bc) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #2280   +/-   ##
=======================================
  Coverage   97.81%   97.81%           
=======================================
  Files         114      114           
  Lines       10266    10266           
=======================================
  Hits        10042    10042           
  Misses        156      156           
  Partials       68       68           

Impacted Files	Coverage Δ
github/event_types.go	100.00% <ø> (ø)

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[gmlewis]

Thank you, @IainSteers !
LGTM.
Merging.