Fix it so that upvoting or downvoting a revealed thresholded comment
doesn't hide it again.
The fix is to explicitly store a `data-show-thresholded` flag on the
comment, instead of manually hiding elements with jQuery, and to morph
the comment HTML instead of replacing it so that the state isn't lost
after voting. Alpine.js is used for this, which isn't strictly necessary,
but is useful to test the library before adopting it on a wider scale.
https://alpinejs.dev/start-here
* Add comment scores.
* Rework voting buttons so that you can click the upvote/downvote
buttons to toggle votes.
* Hide the edit, delete, undelete, and report buttons behind a popup menu.
* Show the upvote/downvote/reply buttons to logged out users. Redirect
them to the login page instead.
Previously thresholded comments were hidden completely. You had to click
the "Show X hidden comments" button to unhide all hidden comments in a
thread. Now it works like this:
* When a comment is below your threshold, the comment text is hidden and
replaced by a `[hidden]` link, which you can click to unhide the comment.
* When a comment is at half your threshold (for example, your threshold
is -8 but the comment is at -4), then the comment is greyed out.
This means that comments aren't completely hidden, they're just
collapsed, so you can see the commenter and the score without unhiding
the comment. It also means you don't have to scroll back up to unhide a
comment, and threads aren't disrupted by comments being secretly
hidden (which is confusing when people are replying to hidden comments,
which forces you to go back up and unhide to find).
