Add CodeBlock import

docs/content/developer/advanced/custom-indexer.mdx

@@ -6,6 +6,7 @@ description: You can build custom indexers using the IOTA micro-data ingestion f
 import Quiz from '@site/src/components/Quiz';
 import questions from '/json/developer/advanced-topics/custom-indexer.json';
 import {Networks} from '@site/src/components/constant'
+import CodeBlock from '@theme/CodeBlock';
 
 You can build custom indexers using the IOTA micro-data ingestion framework. To create an indexer, you subscribe to a checkpoint stream with full checkpoint content. This stream can be one of the publicly available streams from IOTA, one that you set up in your local environment, or a combination of the two.