Set index_heading_entries field in config to index entries with no body

- Previously heading entries were not indexed to maintain search quality
- But given that there are use-cases for indexing entries with no body
- Add a configurable `index_heading_entries' field to index heading entries
- This `TextContentConfig' field is currently only used for OrgMode content

src/utils/rawconfig.py

@@ -18,6 +18,7 @@ class TextContentConfig(ConfigBase):
     input_filter: Optional[str]
     compressed_jsonl: Path
     embeddings_file: Path
+    index_heading_entries: Optional[bool] = False
 
     @validator('input_filter')
     def input_filter_or_files_required(cls, input_filter, values, **kwargs):