feat: add SitemapLoader (#68)

README.md

@@ -294,6 +294,13 @@ To supply your own QnA pair, use the data_type as `qna_pair` and enter a tuple.
 ```python
 app.add_local('qna_pair', ("Question", "Answer"))
 ```
+### Sitemap
+
+To add a XML site map containing list of all urls, use the data_type as `sitemap` and enter the sitemap url. Eg:
+
+```python
+app.add('sitemap', 'a_valid_sitemap_url/sitemap.xml')
+```
 
 ### Reusing a Vector DB