Independent Publisher: Add theme styles to the editor so that fonts match

[scruffian]

Changes proposed in this Pull Request:

This adds the theme styles to the editor so that the frontend and the editor match. Ideally we wouldn't need editor styles at all, but the post title requires them, and maybe other blocks do to...

Related issue(s):

Part of #3280

[jffng]

This fixes the issue of the incorrect fonts loading in the editor.

[jffng]

Should the minor version number be bumped?

[scruffian]

Changed to local file references and bumped the version number.

[scruffian]

I also removed the .edit-post-visual-editor selector from editor-blocks.css. When this file is added as an editor style then the .editor-styles-wrapper prefix is added, so .edit-post-visual-editor won't work. I also renamed .editor-block-list__block to .block-editor-block-list__block since the class has changed names in Gutenberg.

[scruffian]

I updated the approach here to remove as many editor styles as possible. This is ready for another review.

[jffng]

This is being affected in the same way that Penscratch was, where some styles are leaking into the editor UI: