Docs "note" style should have stronger highlighting

Created by: beyang

Currently, aside.node elements in the docs (which correspond to > Markdown blockquotes) are not highlighted in any way. They are indistinguishable from paragraph text. However, they often have important information that a user should notice on the page. For instance:

@francisschmaltz Can we highlight these things by placing them in a yellow rounded-corner box or whatever you think is best as design chief?