[ci] Extend image detection for values.yaml

[jkroepke]

What this PR does / why we need it

Detect images dependencies like this in values.yaml:

helm-charts/charts/kube-prometheus-stack/values.yaml

Lines 2625 to 2628 in 3a15cac

	image:
	registry: registry.k8s.io
	repository: ingress-nginx/kube-webhook-certgen
	tag: v1.5.1 # latest tag: https://github.com/kubernetes/ingress-nginx/blob/main/images/kube-webhook-certgen/TAG

Which issue this PR fixes

(optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close that issue when PR gets merged)

• fixes #

Special notes for your reviewer

Tested: https://regex101.com/r/9R46tF/1

Checklist

• DCO signed
• Chart Version bumped
• Title of the PR starts with chart name (e.g. [prometheus-couchdb-exporter])