Make a new category auto-complete based on JavaScript

[bouncepaw]

Here's how the category auto-complete based on <datalist> tag looks like in an outdated Safari:

After using it for many months, I am very sure it is bad. A JS-based approach similar to the one in Betula should be used.

Why?

1. Every browser renders the autocomplete, and this is fine. But every browser does it in the most obtrusive way out there. I just haven't found a browser where it's fine.
2. For example, my outdated desktop Safari is case-sensitive for Russian strings, but not for English strings. What?? Of course I want to be case-insensitive for all inputs.
3. In Android Vivaldi, the list just pops out on the whole screen, blocking everything. And it does not disappear unless you click something.

Yeah, relying on native elements is fun, but it proved to be bad.