Feature/gutenberg theme support

[saltcod]

Rationale:

Unless we enable responsive-embeds support, we should add our own styles for styling embeds responsively. I've added a new blocks.css file for this. My thought is that if we add more block-specific styles, we can then start splitting this out into more specific partials (perhaps embeds.css in this case).

add_theme_support( 'disable-custom-font-sizes' );
— Disables the custom font size input box.

add_theme_support( 'disable-custom-colors' );
— disables the core colour palette

add_theme_support( 'editor-color-palette', array() );
— if we disable the core colour palette, we need to pass in our own array of (0) colours.

As Damon and I discussed in Slack, further work needs to be broken out into separate issues so we can properly have discussion around them. this is meant to be a few obvious defaults.

[colorful-tones]

Just digging in on this.

1. I would recommend we normalize the user-agent figure element's margin's with this responsive addition. Basically, when I check out your changes in theme scaffold the oembed has side margins. So, I would add to the top of the blocks.css:

   .wp-has-aspect-ratio {
       margin-left: 0;
       margin-right: 0;
   }
   

   I'm attaching a Before and After screenshot to bottom.

2. Adding in add_theme_support( 'disable-custom-font-sizes' );, add_theme_support( 'disable-custom-colors' );, and add_theme_support( 'editor-color-palette', array() ); disables these options from the Gutenberg editor, but already saved content is not affected. We would have to remove the enqueueing of Gutenberg's front-end styles to completely annihilate (should this be the desired approach) the affects of these settings.

   This was not something I had considered before. 🤔

   So, should we take on a redesign with lots of legacy Gutenberg content. And, we install the Theme
   Scaffold with these new filters then the styled content will still exist. I guess this is not so bad, but
   the user expectation might lead to a little confusion.

[timwright12]

@saltcod is there a reason we can't add this stuff into the wordpress.css file?

[saltcod]

@timwright12 we can, but there was thought that this file would grow and it would be nice to have this file as the placeholder for that growth.

[saltcod]

I need to re-followup on this one.

[jeffpaul]

@saltcod any ETA on updating this PR?