Async Tasks docs don't explain what happens if state callbacks are omitted

[caugner]

See: https://lit.dev/docs/data/task/#rendering-tasks

The page lists the state callbacks, but doesn't explain what happens if a state callback is omitted.

In particular, when the same rendering is desired for initial and pending state, do both state callbacks need to be defined? And what happens if a callback is omitted.

[justinfagnani]

If a callback is omitted, it's just not called. Nothing is rendered for that state.

We can mention that in the docs. PRs welcome.