Add installation guide

[afuetterer]

• add "Getting Started" nav
• add install.md
• add link to install guide from readme
• pip (with optional dependencies, e.g. cli)
• uv
• Note: make a venv
• from source with git
• docker/podman from ghcr
• docker image has cli group installed
• Dependencies list
• optional dependency groups
• help with installing docker, podman, etc? footnotes
• add link from first pip install to dependencies section
• add links to sources other guides