docs: Document includes property on getEntries response

Fixes #69

lib/entities/entry.js

@@ -31,6 +31,7 @@ export function wrapEntry (data) {
  * @prop {number} limit
  * @prop {Array<Entities.Entry>} items
  * @prop {Array<Object>=} errors - Array of errors that might occur when retrieving entries.
+ * @prop {Object<Array>=} includes - Object with arrays of includes for Entries and Assets. This will be present if resolveLinks is on, and any linked entries or assets exist. Those links will be resolved in the Entries present in the items array, but they are also present here in raw form.
  * @prop {function(): Object} toPlainObject() - Returns this Entry collection as a plain JS object
  * @prop {function(?function=, space=): Object} stringifySafe(replacer,space) - Stringifies the entry collection, accounting for circular references. Circular references will be replaced with just a Link object, with a <code>circular</code> property set to <code>true</code>. See <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/JSON/stringify">MDN</a> and <a href="https://www.npmjs.com/package/json-stringify-safe">json-stringify-safe</a> for more details on the arguments this method can take.
  */