fix some erros

check if the url exists when downloading resources

fix the error that the mp4 video download link does not exist

fix the error that the mp4 video download link does not exist

Fix coursera-dl to work and major tweaks

Fix:

• fix .unescape error in Python 3.9 and above
• fix course outline pasing error
• fix syntax error
• fix unit test
• fix login failed error

Features:

• add --browser-cookie argument to specify automatically extract CAUTH value from the browser cookie.
• add support for login using browser, and --headless argument can be used to contronl.
• add github actions workflow to run unit test

Refactor:

• rename project
• update python version of support
• move test