Do not include sourcemap files in Service Worker shell

Fixes #534

test/apps/with-sourcemaps-webpack/webpack.config.js

@@ -0,0 +1,73 @@
+const webpack = require('webpack');
+const config = require('../../../config/webpack.js');
+
+const mode = process.env.NODE_ENV;
+const dev = mode === 'development';
+
+module.exports = {
+	client: {
+		entry: config.client.entry(),
+		output: config.client.output(),
+		resolve: {
+			extensions: ['.js', '.json', '.html'],
+			mainFields: ['svelte', 'module', 'browser', 'main']
+		},
+		module: {
+			rules: [
+				{
+					test: /\.html$/,
+					use: {
+						loader: 'svelte-loader',
+						options: {
+							dev,
+							hydratable: true,
+							hotReload: true
+						}
+					}
+				}
+			]
+		},
+		mode,
+		plugins: [
+			dev && new webpack.HotModuleReplacementPlugin(),
+			new webpack.DefinePlugin({
+				'process.browser': true,
+				'process.env.NODE_ENV': JSON.stringify(mode)
+			}),
+		].filter(Boolean),
+		devtool: dev ? 'inline-source-map' : 'source-map'
+	},
+
+	server: {
+		entry: config.server.entry(),
+		output: config.server.output(),
+		target: 'node',
+		resolve: {
+			extensions: ['.js', '.json', '.html'],
+			mainFields: ['svelte', 'module', 'browser', 'main']
+		},
+		module: {
+			rules: [
+				{
+					test: /\.html$/,
+					use: {
+						loader: 'svelte-loader',
+						options: {
+							css: false,
+							generate: 'ssr',
+							dev
+						}
+					}
+				}
+			]
+		},
+		mode: process.env.NODE_ENV
+	},
+
+	serviceworker: {
+		entry: config.serviceworker.entry(),
+		output: config.serviceworker.output(),
+		mode: process.env.NODE_ENV,
+		devtool: 'sourcemap'
+	}
+};