Lint: fix require .js extension

webpack/test.js

@@ -2,7 +2,7 @@
 console.log('Running in test mode'); // eslint-disable-line no-console
 
 const { merge } = require('webpack-merge');
-const sharedConfig = require('./shared.js');
+const sharedConfig = require('./shared');
 
 module.exports = merge(sharedConfig, {
   mode: 'development',