Fix loading opt-in block metadata

Build version of plugin doesn't contain assets/js folder.
We need to copy block.json file with the metadata to assets/dist directory and load it from there.
[MAILPOET-3920]

lib/PostEditorBlocks/WooCommerceBlocksIntegration.php

@@ -59,7 +59,7 @@ class WooCommerceBlocksIntegration {
       '__experimental_woocommerce_blocks_add_data_attributes_to_block',
       [$this, 'addDataAttributesToBlock']
     );
-    $this->wp->registerBlockType(Env::$assetsPath . '/js/src/marketing_optin_block');
+    $this->wp->registerBlockType(Env::$assetsPath . '/dist/js/marketing_optin_block');
     $this->extendRestApi();
   }
 

webpack.config.js

@@ -488,6 +488,14 @@ const marketingOptinBlock = Object.assign({}, wpScriptConfig, {
       requestToExternal,
       requestToHandle,
     }),
+    new WebpackCopyPlugin({
+      patterns: [
+        {
+          from: 'assets/js/src/marketing_optin_block/block.json',
+          to: 'block.json',
+        },
+      ],
+    }),
   ],
 });