title: Add "blocks" in 'settings_schema.json' in shopify theme
body: <p>I am new to Shopify and building my custom theme in Shopify I want to add "blocks" in settings_schema.json as I add in the section schema, Is it possible? if yes then how can I add it? Please help me<br/>
  I have added the following code:</p>
  
  <pre><code>    [
    {
      "name": "theme_info",
      "theme_name": "Slate",
      "theme_version": "0.11.0",
      "theme_author": "Shopify",
      "theme_documentation_url": "https:\/\/shopify.github.io\/slate\/",
      "theme_support_url": "https:\/\/github.com\/Shopify\/slate"
    },
    {
      "name": "Colors",
      "settings": [
        {
          "type": "header",
          "content": "General colors"
        },
        {
          "type": "color",
          "id": "color_theme",
          "label": "Theme color",
          "default": "#efeeeb",
          "info": "Used for theme"
        },
        {
          "type": "color",
          "id": "color_primary",
          "label": "Primary color",
          "default": "#4d4d4d",
          "info": "Used for text links, and primary buttons"
        }
      ],
      "blocks": [
        {
          "type": "product_colors",
          "name": "Product colors",
          "settings": [
            {
              "type": "color",
              "id": "color_label",
              "label": "Color label",
              "default": "red"
            },
            {
              "type": "color",
              "id": "color_code",
              "label": "Color code",
              "default": "#ff0000"
            }
          ]
        }
      ]
    }
  ]
  </code></pre>
  
  <p>But it gives an error: </p>
  
  <blockquote>
    <p>Error: Section 2: 'blocks' is not a valid attribute</p>
  </blockquote>
  
  <p>Any other solutions also appreciated</p>