Save conversation and preset functions

[BaksiLi]

• Implement saving and loading of conversations, just like the web version.
• Built-in conversations like coding assistant, translator etc.
• CLI

cliai chat --preset <preset-name>

[LumenYoung]

Hi BaksiLi, I've created a PR for implementing preset handling here #4. Discussions are welcomed.

[BaksiLi]

Hi BaksiLi, I've created a PR for implementing preset handling here #4. Discussions are welcomed.

I merged your branch to branch dev. It will be merged to main in the upcoming version soon.

Thanks!