feat: allow context to be passed as null

[calthejuggler]

This PR allows context to be passed to the SDKProvider as null. It is then up to the user to reset the context and provide it later. This is an attempt to remove one rerender from static pages on NextJS

[caal-15]

Hi! I think this technically achieves what we want but added some notes on how it maybe could be improved (at least in my opinion)!

Also, do note that this should be a breaking change, since some people may be depending on the context coming from useTreatment never being null :)

[caal-15]

[Question]: Wouldn't it be better to also keep the SDK null until a non-null context is passed (or requested via resetContext)?

[caal-15]

[Suggestion]: I think this implies the only method of replacing the null context is via the resetContext function, while this technically works it could create a disconnect between the context being passed to the provider (i.e. null) and the internal context of the provider (an actual fully functional context).

I think a better approach would be to have an useEffect hook listening to possible changes in the context, so that when the context passed to the provider is no longer null we update the internal values, here's a snippet of how it could potentially work:

export const SDKProvider: FC<SDKProviderProps> = ({
  sdkOptions,
  contextOptions,
  context,
  children,
}) => {
  let contextInitialValue = context;
  let sdkInitialValue = context ? context['_sdk'] : null;
  if (context === undefined) {
    sdkInitialValue = new absmartly.SDK({ retries: 5, timeout: 3000, ...sdkOptions });
    contextInitialValue = sdk.createContext(contextOptions);
  }

  const [context, setContext] = useState<Context | null>(contextInitialValue);
  const [sdk, setSdk] = useState<SDK | null>(sdkInitialValue);

  useEffect(() => {
    if (!!context) {
      setContext(context);
      setSdk(context['_sdk']);
    };   
  }, [context]);
};

You could probably improve performance a bit by memoizing values and such, but this is the gist of it :)