Add block styles (#2662)

This addresses a few issues with Independent Publisher 2. Specifically captions and embeds.

Before: https://d.pr/i/IHESSd
After: https://d.pr/i/JTYmUh

I used Code Snippets to test the block style function.

```
// Add support for Block Styles.
		add_theme_support( 'wp-block-styles' );
```

Fixes
https://github.com/Automattic/themes/issues/2444
https://github.com/Automattic/themes/issues/2454

independent-publisher-2/functions.php

@@ -80,6 +80,9 @@ function independent_publisher_2_setup() {
 	// Load regular editor styles into the new block-based editor.
 	add_theme_support( 'editor-styles' );
 
+	// Add support for Block Styles.
+	add_theme_support( 'wp-block-styles' );
+
 	// Add support for responsive embeds.
 	add_theme_support( 'responsive-embeds' );