feat(onError): introduce onError option

[francoischalifour]

I'm not sure we should introduce this option until somebody needs it, so I only open this PR as a draft.

Description

This adds the onError option to catch errors while fetching suggestions.

Usage

<Autocomplete
  onError={({ state }) => {
    console.error(state.statusContext.error.message);
  }}
  getSources={() => {
    return [
      {
        getInputValue({ suggestion }) {
          return suggestion.query;
        },
        getSuggestions({ query }) {
          return Promise.reject(new Error("Can't fetch suggestions."));
        },
      },
    ];
  }}
/>

Notes

• Perhaps onError is too generic as a name?
• statusContext seems really close to status and context already present in the state object