Webpack 5 support

[kbrownlees]

Looks like a change in webpack 5 may of broken this plugin?

[webpack-cli] TypeError: compiler.apply is not a function
    at cdvAssets.files.forEach (/Users/kieran/work/cloudscape/cloudscape/packages/foreman.safesite-mobile/node_modules/corber-webpack-plugin/index.js:27:16)
    at Array.forEach (<anonymous>)
    at CorberWebpackPlugin.apply (/Users/kieran/work/cloudscape/cloudscape/packages/foreman.safesite-mobile/node_modules/corber-webpack-plugin/index.js:14:19)
    at createCompiler (/Users/kieran/work/cloudscape/cloudscape/packages/foreman.safesite-mobile/node_modules/webpack/lib/webpack.js:71:12)
    at create (/Users/kieran/work/cloudscape/cloudscape/packages/foreman.safesite-mobile/node_modules/webpack/lib/webpack.js:115:15)
    at webpack (/Users/kieran/work/cloudscape/cloudscape/packages/foreman.safesite-mobile/node_modules/webpack/lib/webpack.js:139:31)
    at f (/Users/kieran/work/cloudscape/cloudscape/packages/foreman.safesite-mobile/node_modules/webpack/lib/index.js:35:15)
    at WebpackCLI.createCompiler (/Users/kieran/work/cloudscape/cloudscape/packages/foreman.safesite-mobile/node_modules/webpack-cli/lib/webpack-cli.js:219:24)
    at WebpackCLI.getCompiler (/Users/kieran/work/cloudscape/cloudscape/packages/foreman.safesite-mobile/node_modules/webpack-cli/lib/webpack-cli.js:242:21)
    at process._tickCallback (internal/process/next_tick.js:68:7)