docs：更新文档

node_modules/loader-utils/lib/getCurrentRequest.js

@@ -0,0 +1,16 @@
+'use strict';
+
+function getCurrentRequest(loaderContext) {
+  if (loaderContext.currentRequest) {
+    return loaderContext.currentRequest;
+  }
+
+  const request = loaderContext.loaders
+    .slice(loaderContext.loaderIndex)
+    .map((obj) => obj.request)
+    .concat([loaderContext.resource]);
+
+  return request.join('!');
+}
+
+module.exports = getCurrentRequest;