fix: exit with return code 0, exit early with --help

[karlhorky]

Hi there, I was reading the code for the --help flag and I realized that create-playwright is:

1. Exiting with a non-zero exit code
2. Doing some work to find the root directory and then throwing that away

Both of these seem like unusual patterns.

Some basis for the return code 0 change here:

• https://stackoverflow.com/questions/50565408/should-bash-scripts-called-with-help-argument-return-0-or-not-zero-exit-code