Fix #317: Add styling to block quotes

[Blendify]

Before:

After:

Take note of the comment in the code:

  // For the most part, its safe to assume that sphinx wants you to use a blockquote as an indent. It gets
  // used in many different ways, so don't assume you can apply some fancy style, just leave it be.

Looking at our demo files the only effects it has is on block quotes and line blocks. I can make it only apply to block quotes. AFAIK this currently would cause issues on my website but would like to get some feedback on this.

[Blendify]

My personal preference would be to not add the styling to line blocks