This adds a new powershell install script suitable for running via
irm https://ollama.com/install.ps1 | iex
If you download the script and run '-?' it reports basic usage
information, as well as usage examples for common customization
options. The script is signed as part of the release process
to ensure it can run on a typically configured Windows system.
This does not include doc updates - we can merge those after a release
ships to avoid user confusion.
