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

**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`:

```json
{
"displayHelpMessage": false
}
```

Start by locating Render.displayStats and the default configuration file mentioned in the issue. Trace how configuration options are loaded, add the displayHelpMessage setting there, and verify that setting it to false suppresses the startup help message when no tasks or notes exist.

Written by the indexing model from the issue text.