Add testURL setting to Jest configuration

The default URL `about:blank` will not work with jsdom's strict localStorage
implementation.

Author: yhatt

jest.config.js

@@ -6,5 +6,6 @@ module.exports = {
     '^.*\\.s?css$': '<rootDir>/test/_transformers/css.ts',
   },
   testRegex: '(/(test|__tests__)/(?!_).*|(\\.|/)(test|spec))\\.[jt]s$',
+  testURL: 'http://localhost/',
   moduleFileExtensions: ['ts', 'js', 'json', 'node'],
 }