Support input prompt like llama.cpp

[donge]

Input Prompts

The main program provides several ways to interact with the LLaMA models using input prompts:

• --prompt PROMPT: Provide a prompt directly as a command-line option.
• --file FNAME: Provide a file containing a prompt or multiple prompts.
• --interactive-first: Run the program in interactive mode and wait for input right away. (More on this below.)
• --random-prompt: Start with a randomized prompt.