Add azure auth plugin for AKS cluster

[int128]

Verified with an AKS cluster integrated with AAD.

% kubectl apply -f https://raw.githubusercontent.com/kubernetes/dashboard/v2.0.1/aio/deploy/recommended.yaml

% go run main.go -n kubernetes-dashboard https://kubernetes-dashboard.svc
Forwarding from 127.0.0.1:52935 -> 8443
Open http://localhost:18000
Handling connection for 52935

[codecov-commenter]

Codecov Report

Merging #72 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master      #72   +/-   ##
=======================================
  Coverage   84.84%   84.84%           
=======================================
  Files           1        1           
  Lines          99       99           
=======================================
  Hits           84       84           
  Misses          9        9           
  Partials        6        6           

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 7ebfd00...0991523. Read the comment docs.