JSON error while using "build-args"

## 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

Start by locating the build-args option handling and its usage examples, then reproduce the documented string and array inputs to confirm both parsing failures. Done means an example shows how to pass a build argument and array-form build arguments are accepted without the reported errors.

Written by the indexing model from the issue text.