add env vars declarations and comments for Image Registry user/pw #93

Namespace: <a href="https://detailurl.setting.custom-console-url-namespace.is.not.configured" rel="nofollow">rhtap-shared-team-tenant
PipelineRun: <a href="https://console.redhat.com/application-pipeline/ns/rhtap-shared-team-tenant/pipelinerun/rhtap-task-runner-on-pull-request-fhqfn" rel="nofollow">rhtap-task-runner-on-pull-request-fhqfn

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Red Hat Konflux/rhtap-task-runner-on-pull-request has successfully validated your commit.

Status	Duration	Name
✅ Succeeded	7 seconds	init
✅ Succeeded	10 seconds	clone-repository
✅ Succeeded	7 seconds	prefetch-dependencies
✅ Succeeded	1 minute	build-container
✅ Succeeded	7 seconds	build-image-index
✅ Succeeded	15 seconds	rpms-signature-scan
✅ Succeeded	1 minute	clamav-scan
✅ Succeeded	9 seconds	deprecated-base-image-check
✅ Succeeded	7 seconds	apply-tags
✅ Succeeded	31 seconds	clair-scan
✅ Succeeded	16 seconds	sast-snyk-check
✅ Succeeded	34 seconds	ecosystem-cert-preflight-checks
✅ Succeeded	10 seconds	push-dockerfile
✅ Succeeded	8 seconds	show-sbom