feat: add toc option in transformer node in ingestion pipeline (#11992)

### What problem does this PR solve?

Add TOC (Table of contents) option in Ingestion Pipeline canvas >
Transformer node

### Type of change

- [x] New Feature (non-breaking change which adds functionality)

web/src/locales/en.ts

@@ -1925,6 +1925,7 @@ The Indexer will store the content in the corresponding data structures for the
       keywords: 'Keywords',
       questions: 'Questions',
       metadata: 'Metadata',
+      toc: 'Table of contents',
       fieldName: 'Result destination',
       prompts: {
         system: {