Add a copy button to code blocks

[markijbema]

Especially` in the ask mode it is worthwhile to be able to copy code from a code block easily, because there it is interesting to ask kilo to give multiple alternatives, and then choose one and copy it.

From Discord:
https://discord.com/channels/1349288496988160052/1349288496988160055/1394888075066343525

[kevinvandijk]

Shipped in https://github.com/Kilo-Org/kilocode/releases/tag/v4.94.0