Add loki-stack helm chart

Makefile

production/helm/README.md

production/helm/loki-stack/.helmignore

production/helm/loki-stack/Chart.yaml

production/helm/loki-stack/requirements.yaml

production/helm/loki-stack/templates/NOTES.txt

production/helm/loki-stack/values.yaml

production/helm/loki/.helmignore

production/helm/loki/grafana.yaml

production/helm/loki/values.yaml

production/helm/promtail/.helmignore

production/helm/promtail/templates/_helpers.tpl