Allow bot to feedback on the PDF url given

[rodonguyen]

• Research ways to get the bot to gain access to the PDF. One way we decided is to put the PDF download link in the command since this is simple and straightforward to begin with. So you can follow this direction and find a tutorial that helps you do this.
• Implement in src/discord_bot/:
  • Download PDF
  • Parse PDF
  • Delete PDF
  • Send pdf parsed text to LLM
  • Handle errors