"Search" continues after you navigate away from the page

[NfNitLoop]

To reproduce:

1. On the feed page, start a text-based search.
2. when an item shows up, click the link to navigate to its page.
3. View the network control panel in the browser.

Expected:

• No more search-related traffic

Observed:

• The browser is still loading posts from my feed trying to perform the brute-force search.

This is probably because of the current use of Async Generators that don't have a mechanism to get canceled.

https://seg.phault.net/blog/2018/03/async-iterators-cancellation/ has a good writeup.

Maybe I can just reuse the AbortController and pass that into the async generators, and make sure to abort it when the page is unloaded.

[NfNitLoop]

Related, see: #78 for showing status.