Excessive space around numbered list

[gnprice]

@kasperg reported the following behavior at zulip/zulip#17284:

There are two things that are quite wrong here:

1. There's too much space between the paragraph and the following list.
2. The list items are too deeply indented.

By contrast, we have pretty reasonable behavior with a plain bulleted list. We should use the same spacing for numbered lists as for bulleted lists.

(It's possible the spacing for bulleted lists should be slightly tweaked, too. But first let's make both kinds behave the same way, and then we can tweak them both together.)

A good comparison to look at is the webapp's behavior. See zulip/zulip@03e4ccb which recently adjusted this for the webapp.

[rajprakash00]

@gnprice Can i work on this issue?