docs(exporter): describe directory exporter

Author: dignifiedquire

src/exporters/dir.js

@@ -9,6 +9,16 @@ const switchType = require('../util').switchType
 
 // Logic to export a unixfs directory.
 module.exports = (node, name, dagService) => {
+  // The algorithm below is as follows
+  //
+  // 1. Take all links from a given directory node
+  // 2. Map each link to their full name (parent + link name) + hash
+  // 3. Parallel map to
+  // 3.1. Resolve the hash against the dagService
+  // 3.2. Switch on the node type
+  //      - `directory`: return node
+  //      - `file`: use the fileExporter to load and return the file
+  // 4. Flatten
   return pull(
     pull.values(node.links),
     pull.map((link) => ({