Docs: PING_URL substitution got lost during refactoring, adding it back
Docs: PING_URL substitution got lost during refactoring, adding it back

healthchecks/healthchecks,iphoting/healthchecks,iphoting/healthchecks,iphoting/healthchecks,iphoting/healthchecks,healthchecks/healthchecks,healthchecks/healthchecks,healthchecks/healthchecks