### Summary
An initial pass on smart chunking for RAG applications. Breaks a
document into sections based on the presence of `Title` elements. Also
starts a new section under the following conditions:
- If metadata changes, indicating a change in section or page or a
switch to processing attachments. If `multipage_sections=True`, sections
can span pages. `multipage_sections` defaults to True.
- If the length of the section exceeds `new_after_n_chars` characters.
The default is `1500`. The chunking function does not split individual
elements, so it's possible for a section to exceed that threshold if an
individual element if over `new_after_n_chars` characters, which could
occur with a long `NarrativeText` element.
- Section under `combine_under_n_chars` characters are combined. The
default is `500`.
### Testing
```python
from unstructured.partition.html import partition_html
from unstructured.chunking.title import chunk_by_title
url = "https://understandingwar.org/backgrounder/russian-offensive-campaign-assessment-august-27-2023-0"
elements = partition_html(url=url)
chunks = chunk_by_title(elements)
for chunk in chunks:
print(chunk)
print("\n\n" + "-"*80)
input()
```
