This commit adds return type annotations to the `address`, `routing`, and `co2only` methods in the `CarbonTracer` class. This helps improve code readability and provides better documentation by specifying the expected return types for these methods.
- Updates the installation command in the README file to use the package name "pycarbontracer" instead of the repository URL
- Updates the version number in the "pyproject.toml" file from "0.9.0" to "0.9.1"
