Add option to disable 'type tb --help to get started! ★' when no task has been created

[gantoreno]

Is your feature request related to a problem? Please describe.
Although it's not an issue, the type tb --help to get started! ★ message always shows up when I open a new terminal and there are no tasks/notes created. Sometimes I'd like to suppress this message.

Describe the solution you'd like
I'd like to have a way to disable that message permanently by adding and extra option to the configuration & default configuration file (inserting an extra condition to Render.displayStats to check for this rule).

On ~/.taskbook.json:

{
    "displayHelpMessage": false
}