Upgrade python-scraperlib to 3.x, including CLI support for description / long_description flags

[benoit74]

See openzim/overview#21

[jo780-full]

The changes to be made in scraper.py , entrypoint.py. Kindly assign this task to me

[jo780-full]

I have made the changes by adding a function that handles the checks the description length instead of the if else in the return in
get_zim_info function.

[jo780-full]

also favicon in the make zim file is now illustrations , not longer favicon

[jo780-full]

#183 kindly check this