Add support for transparency and blur from Alfred's theme
`AlfredExtraPane.app` has been updated to support Alfred themes
containing transparency and blur.
- https://github.com/mr-pennyworth/alfred-extra-pane/commit/16e71e0487719ba36fff9d9c4c38027d4c178e1a
- https://github.com/mr-pennyworth/alfred-extra-pane/commit/2295b987af852476e31c30412cf8140504b9f002
Given that the new version of the extra pane renders the window
with appropriate color, and expects the HTML to not have its own
background color, in this change, we update the CSS for dict entries.
