Add a "DisplayName" on ReactReduxContext for DevTools

[pieplu]

What is the current behavior?

ReactReduxContext don't have a DisplayName. It will be usefull on devtools.

Actually it's look's like:

What is the expected behavior?

Insted of "Context.Provider" in devTools, I expect see "ReactRedux.Provider" or "ReactReduxContext.Provider"

React: 16.8
React-redux: 7.1

I will propose a PR

[timdorr]

Thanks, but I don't think we need this.