Parse multiline strings

[go-dockly]

bug report with the following information:

• Operating System (eg. Windows, Linux, Mac)
  macOS
• Terminal Emulator (eg. xterm, gnome-terminal, konsole, ConEmu, Terminal.app, Command Prompt)
  iTerm
• Bug behaviour
  liner terminates parsing the input after \n always not by complete input buffer
• Expected behaviour
  if I paste contents of my clipboard into liner I'd expect the complete content to be parsed by Prompt not just till first line break
• Complete sample that reproduces the bug
  Paste a two line text in to prompt.

[peterh]

Note to whomever implements this: You should probably prevent strings with newlines in AppendHistory to avoid it showing up as multiple entries in the history.