Add _.every doc note on matching empty collections. [ci skip]

lodash.js

@@ -8612,6 +8612,11 @@
      * Iteration is stopped once `predicate` returns falsey. The predicate is
      * invoked with three arguments: (value, index|key, collection).
      *
+     * **Note:** This method returns `true` for
+     * [empty collections](https://en.wikipedia.org/wiki/Empty_set) because
+     * [everything is true](https://en.wikipedia.org/wiki/Vacuous_truth) of
+     * elements of empty collections.
+     *
      * @static
      * @memberOf _
      * @since 0.1.0