Added CSS for quotations

I've decided to use my own quotations rather than the images from Readwise or via Quoteback javascript embeds. It's a little more work, and not as pretty, but it's actual text and doesn't slow things down.

.quote {
  margin-bottom: var(--block-spacing-vertical);
  background: #eee;
  padding: 1em;
  border-radius: 0.5em;
}
.quote figcaption {
	margin: 0.5em;
	text-align: right;
}
.quote blockquote {
  margin: 1em;
}