export USER_AT_HOST="your-user-name-on-host@hostname"
export PUBKEYPATH="$HOME/.ssh/id_rsa.pub"
ssh $USER_AT_HOST "powershell New-Item -Force -ItemType Directory -Path \"\$HOME\\.ssh\"; Add-Content -Force -Path \"\$HOME\\.ssh\\authorized_keys\" -Value '$(tr -d '\n\r' < "$PUBKEYPATH")'"
see also: https://code.visualstudio.com/docs/remote/troubleshooting#_quick-start-using-ssh-keys