fix(ts): improving ObjectID methods return type

Author: leomp12

src/methods/object-id-pad.js

@@ -5,7 +5,7 @@
  * @description Merge received ObjectID string with new index.
  * @param {string} id - Base ID string, 24 digits hexadecimal
  * @param {string} index - The index to be inserted on the end of base ID, creating new ObjectID
- * @returns {string}
+ * @returns {string & { length: 24 }}
  *
  * @example
  * const id = '5ce59fbf887ef430f1f6ed29'

src/methods/random-object-id.js

@@ -3,7 +3,7 @@
  * @memberof ecomUtils
  * @name randomObjectId
  * @description Generate a random object id with 24 chars hexadecimal string.
- * @returns {string}
+ * @returns {string & { length: 24 }}
  *
  * @example
  * ecomUtils.randomObjectId()