Add title option for auto-generated docs

[jpn--]

This small change allows the user to change the documentation page title. This makes it possible to have documentation with a nicer title like "Foo Command Line Interface" rather than something like "python -m Foo"

[tiangolo]

Thank you! I migrated typer-cli to typer itself, it's now part of the same repo. I integrated your changes here: fastapi/typer#782, added tests and docs. And I made you co-author of that commit. 🤓

Given that, I'll close this one here now. Thanks for the contribution! ☕