Update design of lists in content

[gnprice]

The alignment and spacing of lists (<ul> and <ol> elements) is getting an update. We should apply that update.

References

• Sibling issue: #1493
• Web PR: https://github.com/zulip/zulip/pull/34529
• Web issue (covering many other things too): https://github.com/zulip/zulip/issues/22022
• Design thread: #design > updating lists, blockquotes to spec