docs(update): Update User-Defined Function reranker docs with new all_scores and index functions

www/docs/learn/user-defined-function-reranker.md

@@ -146,6 +146,24 @@ get('$.score') * get('$.part_metadata.boost')
 get('$.document_metadata.reviews[0].score', 0)
 ```
 
+#### Get the full list of scores
+
+The `$.all_scores` function retrieves the entire list of scores for all search 
+results in the current ranking. This is useful because it considers the 
+relevance of results in the overall list.
+
+```sql
+get('$.all_scores')
+```
+#### Get the index of the result
+
+The `$.index` function retrieves the index of a result within its original 
+ranking. This is useful for implementing position-aware adjustments, such as 
+favoring higher-ranked results.
+
+```sql
+get('$.index')
+```
 ## Time functions
 
 The following table lists the available time functions that allow you to