feat: add cursor_data to context

[sudo-tee]

This PR enhances the prompt context generated by the template engine by including the current cursor position and the content of the line under the cursor.

[azorng]

Thanks for the PR, this was part of the context some time ago but I removed it because I didn't find it useful and prompts seem to be more effective with less context. If we send cursor data on every prompt, we are giving the llm information that most of the times is not needed, which can impact the focus or the intent of the original query.

If this is really wanted I'm fine adding a context option in config.lua so this behaviour becomes configurable

[sudo-tee]

This is totally reasonable.

I will update the MR with it as an option.

Thanks

[sudo-tee]

I added a config for the cursor_data

I also added a quick unit test around the functionality

[azorng]

awesome, thanks!