Canvas-grab

In this version, we just added a warning about copyright issues. And there's a minor bug fix.
If you do not encounter this issue, you may choose NOT to upgrade.

- Enforce users to review LICENSE before running this program, refer to https://sv.sjtu.edu.cn/ask/?q-248.html and https://github.com/skyzh/canvas_grab/issues/29 for why we enforce such behavior. PLEASE don't upload copyright materials online.
- Some courses do not follow the naming scheme "(2019-2020-2)-AAxxx-2-NAME". We've added support for this.

- show update content when checking update
- "size limit exceed" message will now be correctly counted
- add contributors and add new common issue in readme
- add support for video download and resolve
- add Chinese readme
- release now contain only one bundled executable
- enhance download bar in Windows console
- [dev] GitHub action will now add release in pre-release mode

- add "logging in" message
- add ":" after "New" and "Update" to split change mode and file name
- update readme for more instructive set up guide
- fix encoding issue when creating new config

add check update note

add auto check update

remove config.py from .gitignore