ci: Skip various jobs/steps if coming from a fork #133

Job	Run time
Detect relevant changed files	8s
Build/Publish arm64 Image	6m 29s
Run cargo-udeps	2m 14s
Build/Publish amd64 Image	7m 53s
Package/Publish 0.0.0-pr821 Helm Chart	31s
Publish/Sign 0.0.0-pr821 Index	26s
Run OpenShift Preflight Check for 0.0.0-pr821-arm64	18s
Run OpenShift Preflight Check for 0.0.0-pr821-amd64	20s
Failure Notification	0s
Finished Build and Publish	4s
	18m 23s

Provide feedback