v0.2: TER-249 fix app yaml support in generate command (#84)

There was a bug that'd not allow yaml files in input flags even while having it documented. Reason was the extension value was inaccurately checked for `yaml` or `yml` instead of `.yaml` or `.yml`.
This change fixes the condition, and also adds unit test to assert this use-case.

v0.1: TER-218 Add release workflow for CLI

Added a Github action workflow that is triggered by the creation of
a release. It will build the various OS/Arch combinations of the CLI
and upload a separate .tar.gz/zip for each to the GH release assets.