Adding SOUL.md to the newtype Profile plugin

For the newtype Profile plugin, I’ve started adding SOUL.md, which is Chief’s personality file. Users can modify it as needed.

But to prevent users from breaking it and rendering Chief useless, I chose a two-layer structure:

1. The lower layer: capabilities and the “inner personality,” which cannot be changed and is hard-coded;

2. The upper layer: the “outer personality,” namely the content in SOUL.md, which can be freely edited.