fix: Use clone to avoid pass by reference (#19)

src/index.js

@@ -1,3 +1,4 @@
+import { cloneDeep } from 'lodash';
 import codeSVG from '@plone/volto/icons/code.svg';
 import showcaseSVG from '@plone/volto/icons/showcase.svg';
 
@@ -96,16 +97,15 @@ const applyConfig = (config) => {
   };
 
   // Add Blocks to gridBlock and accordionBlock
+  // It's important to maintain the chain, and do not introduce pass by reference in
+  // the internal `blocksConfig` object, so we clone the object to avoid this.
   ['gridBlock', 'accordion'].forEach((blockId) => {
     const block = config.blocks.blocksConfig[blockId];
     if (block !== undefined) {
-      config.blocks.blocksConfig.gridBlock = {
-        ...config.blocks.blocksConfig.gridBlock,
-        blocksConfig: {
-          ...config.blocks.blocksConfig,
-        },
-        allowedBlocks: [...config.blocks.blocksConfig.gridBlock.allowedBlocks, 'codeBlock', 'mermaidBlock', 'gistBlock'],
-      };
+      block.allowedBlocks = [...block.allowedBlocks, 'codeBlock', 'mermaidBlock', 'gistBlock'];
+      block.blocksConfig.codeBlock = cloneDeep(config.blocks.blocksConfig.codeBlock);
+      block.blocksConfig.mermaidBlock = cloneDeep(config.blocks.blocksConfig.mermaidBlock);
+      block.blocksConfig.gistBlock = cloneDeep(config.blocks.blocksConfig.gistBlock);
     }
   });