Chatbot: History Panel loading state

[kaylachumley]

We need a figma design for a loading state while the chat history is buffering in the left panel. We can use a pf spinner component for this.

example from composer AI mockups:

[kaylachumley]

ready for review in figma https://www.figma.com/design/MSr6kVEOuAxmPOkjg7x8PO/branch/lhJSyFKqcQXZLTxSY61PzH/PatternFly-6%3A-Patterns-%26-Extensions?m=auto&node-id=5190-4959&t=1fH7L5JaXvDxjIZC-1 @andrew-ronaldson

[kaylachumley]

The loading state, per Andrews recommendation, should use a skeleton loader since we are exposing content incrementally and we know what the expected content layout will be every time. Since figma has some limitations with animations and we do not yet support gradient tokens, the figma designs use a flat fill for the skeleton. The actual skeleton loader should adopt the animated gradient that's on org.

Loading State Light Mode:

Loading State Dark Mode: