-h should be a global flag for --help

[case-fastly]

Is your feature request related to a problem? Please describe.

It's common and conventional for CLI tools to accept -h as a shortcut for invoking --help globally.

But we don't currently support it:

GLOBAL FLAGS
      --help             Show context-sensitive help.
  -d, --accept-defaults  Accept default options for all interactive prompts
                         apart from Yes/No confirmations
  -y, --auto-yes         Answer yes automatically to all Yes/No confirmations.
                         This may suppress security warnings
      --debug-mode       Print API request and response details (NOTE:
                         can disrupt the normal CLI flow output formatting)
      --enable-sso       Enable Single-Sign On (SSO) for current profile
                         execution (see also: 'fastly sso')
  -i, --non-interactive  Do not prompt for user input - suitable for CI
                         processes. Equivalent to --accept-defaults and
                         --auto-yes
  -o, --profile=PROFILE  Switch account profile for single command execution
                         (see also: 'fastly profile switch')
  -q, --quiet            Silence all output except direct command output.
                         This won't prevent interactive prompts (see:
                         --accept-defaults, --auto-yes, --non-interactive)
  -t, --token=TOKEN      Fastly API token (or via FASTLY_API_TOKEN)
  -v, --verbose          Verbose logging

Perhaps there are -h conflicts with subcommands?

Describe the solution you'd like

I'd like fastly -h to work globally as a shortcut for showing help text.

Describe alternatives you've considered

n/a

Additional context

n/a