Fix warnings when building Docker image
3 warnings found (use --debug to expand):
- FromAsCasing: 'as' and 'FROM' keywords' casing do not match (line 1)
- LegacyKeyValueFormat: "ENV key=value" should be used instead of legacy "ENV key value" format (line 8)
- LegacyKeyValueFormat: "ENV key=value" should be used instead of legacy "ENV key value" format (line 23)