Update dependency clean-webpack-plugin to v3

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This PR contains the following updates:

Package	Type	Update	Change
clean-webpack-plugin	dependencies	major	^2.0.1 -> ^3.0.0

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Release Notes

johnagan/clean-webpack-plugin

v3.0.0

Compare Source

• Removed Node 6 support
• Removed webpack 2 support
• cleanOnceBeforeBuildPatterns use emit hook instead of compile
• Do not clean files if webpack errors are present during initial build
• Replaced default export with named export CleanWebpackPlugin

// es modules
import { CleanWebpackPlugin } from 'clean-webpack-plugin';

// common js
const { CleanWebpackPlugin } = require('clean-webpack-plugin');

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