Bug Fixes

• Fixed pdm venv activate, to also work for windows. And added documentation on how to authenticate to Azure Artifacts (#2851)
• Don't show unsupported formats in pdm export. (#2877)
• Proxy (HTTP_PROXY env vars) settings are ignored for custom indexes. (#2880)
• Fix the quoting of venv activate command for powershell. (#2881)
• Raise an error if the package given by pdm update does not exist in the select dependency group but in other groups. (#2885)