Add extracted source directory and README navigation

extracted-source/node_modules/undici/lib/web/fileapi/symbols.js

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+'use strict'
+
+module.exports = {
+  kState: Symbol('FileReader state'),
+  kResult: Symbol('FileReader result'),
+  kError: Symbol('FileReader error'),
+  kLastProgressEventFired: Symbol('FileReader last progress event fired timestamp'),
+  kEvents: Symbol('FileReader events'),
+  kAborted: Symbol('FileReader aborted')
+}