Add 127.0.0.1 to allowlist for source map fetch

Summary:
Adds ipv4 localhost representation (127.0.0.1) to allowlisted hostnames for the inspector-proxy, to allow for proxied network requests fetching source maps.

Changelog:
[General][Fixed] Allow source map fetching in the inspector proxy from 127.0.0.1

Reviewed By: motiz88

Differential Revision: D52112849

fbshipit-source-id: e6d45fa2fdfd570b7ab4f36121ba615c9b06d442

packages/dev-middleware/src/inspector-proxy/Device.js

@@ -674,7 +674,7 @@ export default class Device {
   // Fetch text, raising an exception if the text could not be fetched,
   // or is too large.
   async _fetchText(url: URL): Promise<string> {
-    if (url.hostname !== 'localhost') {
+    if (!['localhost', '127.0.0.1'].includes(url.hostname)) {
       throw new Error('remote fetches not permitted');
     }