Support Custom CSS in Chainlit Configuration for TaskWeaver UI

This PR adds support for specifying a custom CSS file in the Chainlit configuration for TaskWeaver. This feature allows developers to easily customize the appearance of the TaskWeaver UI without modifying the core CSS files. By specifying the path to a custom CSS file in the .chainlit/config.toml, developers can override the default styles to match their branding or user interface requirements.

playground/UI/.chainlit/config.toml

@@ -57,7 +57,7 @@ hide_cot = false
 
 # Specify a CSS file that can be used to customize the user interface.
 # The CSS file can be served from the public directory or via an external link.
-custom_css = "/public/style_v1.css"
+custom_css = "path/to/your/custom.css"
 
 # Override default MUI light theme. (Check theme.ts)
 [UI.theme.light]