Installation instructions are outdated.

From Python version 3.11 one can't directly use pip.

```
➜ ~ pip install notebook
error: externally-managed-environment

× This environment is externally managed
╰─> To install Python packages system-wide, try apt install
python3-xyz, where xyz is the package you are trying to
install.

If you wish to install a non-Debian-packaged Python package,
create a virtual environment using python3 -m venv path/to/venv.
Then use path/to/venv/bin/python and path/to/venv/bin/pip. Make
sure you have python3-full installed.

If you wish to install a non-Debian packaged Python application,
it may be easiest to use pipx install xyz, which will manage a
virtual environment for you. Make sure you have pipx installed.

See /usr/share/doc/python3.11/README.venv for more information.

note: If you believe this is a mistake, please contact your Python installation or OS distribution provider. You can override this, at the risk of breaking your Python installation or OS, by passing --break-system-packages.
hint: See PEP 668 for the detailed specification.
```

and need to run `pipx install notebook` to install it.

Should I submit a pull request for the change?

Locate the installation instructions in the site content and read the current pip command. Update the guidance to address Python 3.11's externally managed environment and the reported pipx installation path, then confirm the instructions cover the error shown in the issue.

Written by the indexing model from the issue text.