Add "always push on PR" flag into config

[vpavlin]

Is your feature request related to a problem? Please describe.
For some repositories I always run /deploy to get image pushed to quay.io to be able to easily test the changes. I

Describe the solution you'd like
I'd like to be able to set a configuration which will result for the pipeline to always push the PR build to registry without the need to add /deploy comment

e.g.

push_on_pr: true

Ideally, the pipeline should also comment on the PR when the push is done and it should provide a link to the new image

Describe alternatives you've considered
Keep using the /deploy command. Although possible, it is not a good user experience

Additional context

The image should be also deleted from the registry when the PR is merged to make sure the image repository is not clutterred (see #52)

[harshad16]

/kind feature

[harshad16]

Thanks for the feature requests, the following step would be implemented for this feature.
Step for creating the task to serve the feature:

• create the configuration required on the configuration file.
• Modify the pull request build pipeline tasks step to push to the registry if this configuration is set.

[sesheta]

Issues go stale after 90d of inactivity.
Mark the issue as fresh with /remove-lifecycle stale.
Stale issues rot after an additional 30d of inactivity and eventually close.

If this issue is safe to close now please do so with /close.

/lifecycle stale

[harshad16]

/remove-lifecycle stale

[sesheta]

Issues go stale after 90d of inactivity.
Mark the issue as fresh with /remove-lifecycle stale.
Stale issues rot after an additional 30d of inactivity and eventually close.

If this issue is safe to close now please do so with /close.

/lifecycle stale

[sesheta]

Stale issues rot after 30d of inactivity.
Mark the issue as fresh with /remove-lifecycle rotten.
Rotten issues close after an additional 30d of inactivity.

If this issue is safe to close now please do so with /close.

/lifecycle rotten

[harshad16]

/lifecycle frozen