Support build hooks

[DimitarTachev]

Is your feature request related to a problem? Please describe.
We are not able to implement something like a cloud builds solution based on CLI hooks.

Describe the solution you'd like
We could expose a "build" hook in order to allow overriding the CLI logic with a custom one.

[rosen-vladimirov]

A sample demonstrating the hooks usage can be found here: https://github.com/rosen-vladimirov/app-build-hooks