Spam filter documentation

[Marvin-Brouwer]

Is your feature request related to a problem? Please describe.
I have no idea why my tweet isn't retweeted.
It could be because of the bot being blocked (#10) but I also could've just violated some rule in the spam filter.
Currently, I have no idea. And I don't really understand what it does from looking at the code.

Describe the solution you'd like
Please add spamfilter rules to the readme or a separate markdown so people can check them against their tweets.

Describe alternatives you've considered
I see you have a spam_filter.ipynb, maybe it's cool to add one where you can supply a URL to a tweet and have it validated?

Additional context
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