fix(karma-webpack): normalize paths to be compatible with windows

Author: igomezal

lib/karma-webpack.js

@@ -82,6 +82,8 @@ function preprocessorFactory(config, emitter) {
     controller.karmaEmitter = emitter;
   }
 
+  const normalize = (file) => file.replace(/\\/g, '/');
+
   const transformPath =
     config.webpack.transformPath ||
     ((filepath) => {
@@ -93,7 +95,7 @@ function preprocessorFactory(config, emitter) {
   return async function processFile(content, file, done) {
     await controller.bundle();
 
-    file.path = transformPath(file.path); // eslint-disable-line no-param-reassign
+    file.path = normalize(transformPath(file.path)); // eslint-disable-line no-param-reassign
 
     const bundleContent = controller.bundlesContent[path.parse(file.path).base];
     done(null, bundleContent);