Add to boost parameter to the prefix query

Signed-off-by: Yuki Imamura <[email protected]>

Author: imamuray

_query-dsl/term/prefix.md

@@ -63,8 +63,9 @@ The `<field>` accepts the following parameters. All parameters except `value` ar
 Parameter | Data type | Description
 :--- | :--- | :---
 `value` | String | The term to search for in the field specified in `<field>`.
+`boost` | Floating-point | Boosts the query by the given multiplier. Useful for searches that contain more than one query. Values in the [0, 1) range decrease relevance, and values greater than 1 increase relevance. Default is `1`. 
 `case_insensitive` | Boolean | If `true`, allows case-insensitive matching of the value with the indexed field values. Default is `false` (case sensitivity is determined by the field's mapping).
 `rewrite` | String | Determines how OpenSearch rewrites and scores multi-term queries. Valid values are `constant_score`, `scoring_boolean`, `constant_score_boolean`, `top_terms_N`, `top_terms_boost_N`, and `top_terms_blended_freqs_N`. Default is `constant_score`.
 
 If [`search.allow_expensive_queries`]({{site.url}}{{site.baseurl}}/query-dsl/index/#expensive-queries) is set to `false`, prefix queries are not run. If `index_prefixes` is enabled, the `search.allow_expensive_queries` setting is ignored and an optimized query is built and run.
-{: .important}
+{: .important}