iOS: save video file to gallery should be optional

[chriskhongqarma]

Feature Request

Motivation Behind Feature

Currently, the plugin saves video into gallery by default on iOS. Developers should have the control over whether the app should save the generated video into gallery or not.

Feature Description

a new param saveToGallery should be added with 2 values: 1 (save file to gallery) or 0 (not save file to gallery)
This feature is not intended on Android because since Android 11, if we save the file into gallery (generated by the camera app), our app will not be able get access to that file. Therefore, file should be saved into a FileProvider, which is suggested in #215 PR.