JSON error while using "build-args"

[swetha-sundar]

Issue

When you pass a string with KeyValue pairs to the build-args option, fails with:

parse error: Invalid numeric literal at line 1, column 5

When you pass an array with KeyValue pairs to the build-args option, fails with:

Missed comma between flow collection entries when using fngetatt in yaml

Todo

1. Add an example on how you would pass a build-arg
2. Add support for arrays for build-arg option

[conor-naranjo]

I ran into this same thing and opened a PR to update the README with an example of using build args: https://github.com/Azure/acr-build/pull/8