Adding documentation

docs/realm.js

@@ -285,6 +285,14 @@ class Realm {
      */
     compact() {}
 
+    /**
+     * Computes the aggregated size of all objects and their history in the Realm.
+     *
+     * Note that this will traverse the Realm and might be expensive for large Realms.
+     * @returns {number} the computed size in bytes.
+     */
+    computeSize() {}
+
     /**
      * Writes a compacted copy of the Realm to the given path.
      *
@@ -456,4 +464,3 @@ class Realm {
  *   any object of this type from inside the same Realm, and will always be _optional_
  *   (meaning it may also be assigned `null` or `undefined`).
  */
-