Fix getting-started.md add project will meet argument mismatch

From the output of docker compose run --rm web bundle exec rake --tasks, there are two commands can be used to add project:

register[project_name] and register_project[project_name,access_token]

With the command in getting-started.md will actually get an error says 'Wrong number of arguments', so this patch changes the command to register

Signed-off-by: AlanJager alanjager@outlook.com