:zap: Implement chunked embed message

[Sigmanificient]

When the bot is run for the first time, all homeworks & grades are fetched and bulk send within the configured channels.
However, every embed is send within its own message which is a waste considering every message can contains up to 5 embeds.

Implementing such a feature would make the first fetch process 5 times faster and thus could avoiding unwanted ratelimits if the numbers of homework/notes is small enough.

from how-do-i-split-a-list-into-equally-sized-chunks

def chunks(lst, n):
    """Yield successive n-sized chunks from lst."""
    for i in range(0, len(lst), n):
        yield lst[i:i + n]