Add http.client.prefetch op

Author: Luca Forstner

develop-docs/sdk/telemetry/traces/span-operations.mdx

@@ -47,6 +47,7 @@ If a span operation is not provided, the value of `default` is set by Relay. The
 |            | ui.action.click           |                                                                                                                                                                                          |
 | http       |                           |                                                                                                                                                                                          |
 |            | http.client               |                                                                                                                                                                                          |
+|            | http.client.prefetch      | Spans for requests that prefetch data or other pages.                                                                                                                                    |
 |            | http.graphql.query        |                                                                                                                                                                                          |
 |            | http.graphql.mutation     |                                                                                                                                                                                          |
 |            | http.graphql.subscription |                                                                                                                                                                                          |