Update .gitlab-ci.yml

1 job for master in 1 minute and 14 seconds (queued for 1 second)
Status Job ID Name Coverage
  Build
failed #2042
Docker
Linux client build

00:01:14

 
Name Stage Failure
failed
Linux client build Build
    subprocess.run(['npm'] + commands, cwd=self.bulma_dir)
File "/usr/local/lib/python3.7/subprocess.py", line 472, in run
with Popen(*popenargs, **kwargs) as process:
File "/usr/local/lib/python3.7/subprocess.py", line 775, in __init__
restore_signals, start_new_session)
File "/usr/local/lib/python3.7/subprocess.py", line 1522, in _execute_child
raise child_exception_type(errno_num, err_msg, err_filename)
FileNotFoundError: [Errno 2] No such file or directory: 'npm': 'npm'
ERROR: Job failed: exit code 1