"Get Alt Text" should print text in a code block, not a quote block

[AverageHelper]

Currently, Discord treats alt text as-is as plaintext in the context of image descriptions. But when CSBot sends that alt text as-is in a Discord message, Discord treats the payload as markdown. This leads to lossy conversions, since copying the text of the message does not convert the formatted message back into markdown plaintext.

Proposed solution: Instead of the current quote block (> ) format, we should instead render the alt text in a code block (```) between triple backticks. The layout is somewhat ugly, but at least the alt text would be copyable without losing precision.

If sighted users want a pretty alt text readout, they can enable Discord's own view, which can be enabled in Settings > Text & Images > With image descriptions.