Accept legacy "ranges" additionally to "leaves" (#1990)

* Accept ranges additionally to leaves

For compatibility with older slate JSON documents, additionally to
the new "leaves" property, also accept "ranges" with a deprecation
warning.

* Fix accepting JSON arrays for "ranges" compatibility

packages/slate/src/models/text.js

@@ -86,7 +86,20 @@ class Text extends Record(DEFAULTS) {
     }
 
     const { key = KeyUtils.create() } = object
-    let { leaves = List() } = object
+    let { leaves } = object
+
+    if (!leaves) {
+      if (object.ranges) {
+        logger.deprecate(
+          'slate@0.27.0',
+          'The `ranges` property of Slate objects has been renamed to `leaves`.'
+        )
+
+        leaves = object.ranges
+      } else {
+        leaves = List()
+      }
+    }
 
     if (Array.isArray(leaves)) {
       leaves = List(leaves.map(x => Leaf.create(x)))