Support STDIN input

[artursouza]

Add support for STDIN input like:

echo "..." | bicep build - or echo "..." | bicep build

[alex-frankel]

@artursouza - we are triaging all of our issues. Is supporting stdin still relevant? If so, can you provide an example for where this would be used.

[artursouza]

@alex-frankel This can be used for scenarios where user has a single file to be built and the output to be used in another command without creating a temporary file. If bicep deploys directly from a bicep file, then this issue is less relevant. In other words, accepting stdin input enables users to deploy their bicep files without creating a temporary file.