[Feature Request]: Create a print method for the `teal_app` object

### Feature description

The app object created using the `init` function is a list of UI and Server functions. It will be nice to have a print method for this object.

Proposal:
```
TEAL APPLICATION
|-UI
| |-Title: teal app title (without favicon)
| |-Header: Show this row if the header is set.
| L-Footer: Show this row if the footer is set.
L-Server
|-Data: list of objects from the `teal_data` object
L-Modules: Label of the modules
```

Please also write a unit test for the format method (refer to the module's format function).

### Code of Conduct

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### Contribution Guidelines

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### Security Policy

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