Add two footer layout options to theme

Closes #3520642

components/block/copyright/copyright.component.yml

+$schema: https://git.drupalcode.org/project/drupal/-/raw/10.1.x/core/modules/sdc/src/metadata.schema.json
+
+name: mainblock
+label: 'Main Block'
+description: 'Generic block component with optional title and content.'
+category: 'Blocks'
+
+schema:
+  properties:
+    plugin_id:
+      type: string
+      description: 'The ID of the block implementation.'
+      default: ''
+    label:
+      type: string
+      description: 'The configured label of the block.'
+      default: ''
+    configuration:
+      type: object
+      properties:
+        provider:
+          type: string
+          description: 'The module or provider of the block.'
+          default: 'custom'
+    title_prefix:
+      type: string
+      description: 'Additional markup before the block title.'
+      default: ''
+    title_suffix:
+      type: string
+      description: 'Additional markup after the block title.'
+      default: ''
+    content:
+      type: string
+      description: 'The main content of the block.'
+      default: '<p>Block content here.</p>'