Flagged module as side effect free to enhance tree shaking

[kaa4ever]

Added sideEffects flag to package.json to allow the tree shaking feature of webpack to totally disregard this module when imported.

A somewhat normal use case of redux-logger could be:

import { createStore, applyMiddleware } from 'redux';
import thunkMiddleware from 'redux-thunk';
import { createLogger } from './redux-logger';
import Reducer from './Reducer';

let store = createStore(Reducer, applyMiddleware(thunkMiddleware));

if (process.env.NODE_ENV !== 'production') {
   const loggerMiddleware = createLogger();
   store = createStore(Reducer, applyMiddleware(thunkMiddleware, loggerMiddleware));
}

When building for production, current Webpack behavior is to exclude anything inside the process.env.NODE_ENV !== 'production' conditional, but not remove the import { createLogger } from './redux-logger';. Since we are not using the logger in any way, it would be nice to totally disregard it from the production build. Adding the "sideEffects": false flag to package.json will achieve exactly that.

[codecov-io]

Codecov Report

Merging #313 into master will not change coverage.
The diff coverage is n/a.

@@          Coverage Diff          @@
##           master   #313   +/-   ##
=====================================
  Coverage      82%    82%           
=====================================
  Files           5      5           
  Lines         150    150           
=====================================
  Hits          123    123           
  Misses         27     27

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