Feature/410 button block

[ravewebdev]

References https://github.com/WebDevStudios/nextjs-wordpress-starter/issues/410

Description

Updates hex color filter:

• Makes filter name more generic
• Allows for applying filter to an array of blocks
• Adds filter on array of blocks to receive hex colors

Screenshots

Steps To Verify Feature

Edit a post (e.g., https://nextjsdevstart.wpengine.com/wp-admin/post.php?post=442&action=edit), view in code editor, and confirm hex color attributes are being generated for color presets.