fix: refactor code to use getDerivedStateFromProps

[AdrianInsua]

This pr will fix #624

In order to do this the code is refactored to use static getDerivedStateFromProps. Considering that the method is static i've moved the methods used inside old willReceiveProps out of the class to avoid repeated code (because we can't call this in static methods).

Also i've moved justPressedUpDown justMouseEntered justSelectedSuggestion into state to acces them in the static method.

Finally i've added a new state variable prevSuggestions to emulate prevProps.suggestions behaviour.

The demo page works fine, but i had some problems with prettier script on build process
(but it works ok without it).

I`m not a React developer so please check the code and let me know if something is wrong

[FullstackJack]

LGTM

[TaiWilkin]

@AdrianInsua Is this still in-progress?

[AdrianInsua]

@TaiWilkin the PR was done several months ago, but it seems to have conflicts now, as soon as i have some free time i will fix them

[lregla]

@pimterry @FullstackJack @AdrianInsua
What steps need to take place at this point in time in order to merge in this PR (other than the obvious merge conflict)?
I am seeing a much more severe StrictMode issue (in line with #624) on React version 17.0.1 with react-autosuggest 10.0.4

Warning: Using UNSAFE_componentWillReceiveProps in strict mode is not recommended and may indicate bugs in your code.
Warning: Cannot update during an existing state transition (such as within `render`). Render methods should be a pure function of props and state.