fix: add type definition of AV.Query#sizeEqualTo (#662)

Author: sdjdd

src/query.js

@@ -597,7 +597,7 @@ module.exports = function(AV) {
        * Add a constraint to the query that requires a particular
        * <strong>array</strong> key's length to be equal to the provided value.
        * @param {String} key The array key to check.
-       * @param value The length value.
+       * @param {number} value The length value.
        * @return {AV.Query} Returns the query, so you can chain this call.
        */
       sizeEqualTo: function(key, value) {

storage.d.ts

@@ -601,6 +601,7 @@ export class Query<T extends Queriable> extends BaseQuery<T> {
   near(key: string, point: GeoPoint): this;
   notContainedIn(key: string, values: any[]): this;
   notEqualTo(key: string, value: any): this;
+  sizeEqualTo(key: string, value: number): this;
   startsWith(key: string, prefix: string): this;
   withinGeoBox(key: string, southwest: GeoPoint, northeast: GeoPoint): this;
   withinKilometers(key: string, point: GeoPoint, maxDistance: number): this;