fix first y-array test

src/Type/YMap.js

@@ -3,6 +3,25 @@ import Item from '../Struct/Item.js'
 import ItemJSON from '../Struct/ItemJSON.js'
 
 export default class YMap extends Type {
+  toJSON () {
+    const map = {}
+    for (let [key, item] of this._map) {
+      if (!item._deleted) {
+        let res
+        if (item instanceof Type) {
+          if (item.toJSON !== undefined) {
+            res = item.toJSON()
+          } else {
+            res = item.toString()
+          }
+        } else {
+          res = item._content[0]
+        }
+        map[key] = res
+      }
+    }
+    return map
+  }
   set (key, value) {
     let old = this._map.get(key)
     let v