Update readme for concurrent rendering

[webbertakken]

React "Concurrent mode" is now "concurrent rendering".

We might also refer to the new documentation blog page for react 18 but it is much more generic, so perhaps keep it as is for now.

Unless I understand ObservableStatus<T> incorrectly somehow, we need to destructure data: T. I updated the doc accordingly.

Description

Code sample

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[webbertakken]

@googlebot I signed it!

[jhuleatt]

Thank you @webbertakken!