Improve discoverability of loading state property

[LLCampos]

Right now its really hard to discover that its possible to do #default="{ state: { loading } }" in your FormKit element.

• Its not mentioned in the docs
• Its not in the FormKitFrameworkContextState interface
• It only appears in the state object when the form starts loading

Context: this Discord conversation.

[justin-schroeder]

It is here: https://formkit.com/api-reference/context#state, but yeah, I agree it should be in more places 👍