Update introduction.md

[hexmind]

fix "It's as simple as 1-2-3"

$ wget https://raw.githubusercontent.com/kubernetes/kompose/master/examples/docker-compose-v3.yaml
$ kompose up
FATA No 'docker-compose' file found: stat docker-compose.yaml: no such file or directory 

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[cdrage]

Thanks! Sorry about the delay. 👍