x/pkgsite: readme markdown lists aren't rendered as html lists

[willfaught]

What is the URL of the page with the issue?

https://pkg.go.dev/github.com/google/go-cmp/cmp

What is your user agent?

Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/15.6 Safari/605.1.15

Screenshot

What did you do?

Went to https://pkg.go.dev/github.com/google/go-cmp/cmp

What did you expect to see?

HTML lists:

• When the default behavior of...

What did you see instead?

Middle dot approximation of HTML lists:

• When the default behavior of...