Add basic e2e tests

[dimabru]

Is your feature request related to a problem? Please describe.
We currently don't have any tests to the cli. This makes it relatively unstable

Describe the solution you'd like
Add some basic e2e tests to go over some scenarios of usage of the cli
Tests should run on PR during the CI workflow

Run the following and make sure the output is correct

1. Main flow

allero fetch github allero-io/demo
allero fetch gitlab allero/demo
allero validate

2. Validate local folder
   Add some test workflows to a local folder and run

allero validate [path-to-local-folder]

3. Fetch from remote url

allero fetch https://github.com/allero-io/demo https://gitlab.com/allero/demo
allero validate