Fix list indentation in TOC (index.md)

[teohhanhui]

List items may consist of multiple paragraphs. Each subsequent paragraph in a list item must be indented by either 4 spaces or one tab

http://daringfireball.net/projects/markdown/syntax#list

Also see Python-Markdown/markdown#3 (comment)

[soyuka]

You will always amaze me with your RFC knowledge \o/

[teohhanhui]

Not an RFC, but oh well... Motivation: I was trying to view the docs on GitHub but noticed that it's one long, flat list. 😅

I also sneaked in another neat trick: Indenting the body of the list item. It looks super neat but renders the same. Especially useful when the body spans multiple paragraphs.

[dunglas]

Good to know! Thanks.