Customize chat template

[helins]

A simple but potentially killer feature would be to allow customizing the chat template. For instance, that would allow interfacing more directly with markdown-based note taking app such as Obsidian and Logseq. Users could prepare the header of the chat file with things like tags. I think having chats in an app like Obsidian would be terrific.

It seems like it would require only simple changes:

• Replace chat_template with a function. The default one would keep the current behavior.
• is_chat seems overly cautious. Why must the file contain - file: ...? Or even a title? Being in the chat dir is the most important factor. For instance, it would suffice that the plugin splits on the first --- in any MD file in the chat dir, assuming what is before is a header to discard and what is after is the chat history to use. Or perhaps I am not considering something :)