Add alternative to pip3 install of cargo lambda

[Bryson14]

Another way to manage executable pip packages is with uv which has been very popular and helpful in the python community.

📬 *Issue #, if available:*

Small issue, When running `pip3 install .....` it shows this error about system vs user installation:

rror: 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/python3.12/README.venv for more information.

✍️ *Description of changes:*

Experienced python users might already know that they can use `uv` to install and load python packages from pip as executable. But for those that don't know, adding this line can be a helpful alternative that doesn't show installation errors, reducing any friction to rust or python developers.

🔏 *By submitting this pull request*

- [x] I confirm that I've ran `cargo +nightly fmt`.
- [x] I confirm that I've ran `cargo clippy --fix`.
- [x] I confirm that I've made a best effort attempt to update all relevant documentation.
- [x] I confirm that my contribution is made under the terms of the Apache 2.0 license.

[calavera]

Uv is great, but it’s not as standard as pip, so at least, you’d have to explain how to install Uv first. The paragraph below already has a link with additional installation methods, it might be better to pick from that list:

https://www.cargo-lambda.info/guide/installation.html

Installation scripts is probably what people are more used to which can be found here:

curl -fsSL https://cargo-lambda.info/install.sh | sh

For Windows/Powershell specifically:

irm https://cargo-lambda.info/install.ps1 | iex