Scrape categories and topics for `news.py`

[tianyizheng02]

We should scrape [the categories and topics]. We have no idea what the maintenance of this repo will look like over time. It's certainly had its lulls over time, so let's make it withstand the lack of us

Originally posted by @RitwikGupta in #203 (comment)

In #203, I rewrote news.py to scrape Pitt news articles from the Pittwire website, but I hard-coded the list of news categories and topics. We should scrape these values instead so that we don't have to keep them updated ourselves. Ideally, news.py should only scrape these values once, when the users uses a function from the module for the first time, so that the values are available for all subsequent function calls.

[tianyizheng02]

Opened an issue for this task in case anyone else wanted to work on it

[timparenti]

Should this really be on import, or should it be on use?

[tianyizheng02]

Both would technically work, but yeah it'll probably be better if they were imported on use, if for no reason than to make the code easier to test.