Add "Reviewed by you" filter for pull requests (#22927)

This includes pull requests that you approved, requested changes or
commented on. Currently such pull requests are not visible in any of the
filters on /pulls, while they may need further action like merging, or
prodding the author or reviewers.

Especially when working with a large team on a repository it's helpful
to get a full overview of pull requests that may need your attention,
without having to sift through the complete list.

templates/swagger/v1_json.tmpl

@@ -2366,6 +2366,12 @@
             "name": "review_requested",
             "in": "query"
           },
+          {
+            "type": "boolean",
+            "description": "filter pulls reviewed by you, default is false",
+            "name": "reviewed",
+            "in": "query"
+          },
           {
             "type": "string",
             "description": "filter by owner",