v0.2.3 release

Version 0.2.3 is the official version of this project. We have added support for browser extensions, so you no longer need the complicated Tampermonkey script installation process. Meanwhile, tampermonkey script is still under supportment. Maybe there is soambody tending to Tampermonkey just like me.

Full Changelog: https://github.com/hazuki-keatsu/xuexitong-ppt-downloader/commits/0.2.3