WIP: Allow to export chats

[gmatheu]

Still WIP

I want to be able to export chats for 2 main reasons:

• In case of working specifically on a project, be able to track the history of the conversation for the other committers (e.g.: in the repository).
  I think this might be useful for other people to understand how you get to a specific solution.

I did json at first, but I guess it might be more convenient to use Markdown to make it more readable straight from the browser.

• To be able to import (inter-exchange in general) chats from elia in other tools (such as ChatGPT neovim's plugin).

Sometimes I like to work inside the editor and sometimes it more comfortable to use just the terminal. I think it might be nice to be able to use the same conversation.
An alternative to this might be to have some hooks integrating other tools (such a a 'remote' mode for elia)