Add composer.lock to Dockerfile

3 jobs for master in 16 seconds (queued for 2 seconds)
Name Stage Failure
failed
build Build
  ...20d11238256a4a"				"shasum": ""			},	       
---------------------^
Expected one of: 'EOF', '}', ':', ',', ']'


install [--prefer-source] [--prefer-dist] [--dry-run] [--dev] [--no-dev] [--no-custom-installers] [--no-autoloader] [--no-scripts] [--no-progress] [--no-suggest] [-v|vv|vvv|--verbose] [-o|--optimize-autoloader] [-a|--classmap-authoritative] [--apcu-autoloader] [--ignore-platform-reqs] [--] [<packages>]...

The command '/bin/sh -c composer install --no-dev' returned a non-zero code: 1
ERROR: Job failed: exit code 1