add reviewer assigning

TODO.md

@@ -75,7 +75,7 @@ editing are already implemented.
 ## Data completeness and compatibility
 
 - Paginate or explicitly mark truncation for the remaining fixed-size
-  connections: assignees, labels, review requests, latest reviews, repository
+  connections: labels, review requests, latest reviews, repository
   rulesets, and rules within a ruleset.
 - Model pending reviews, minimized comments, deleted comments/users, edited
   timestamps, and explicit reply relationships.
@@ -92,9 +92,8 @@ editing are already implemented.
 
 ## Write roadmap
 
-- Add fuzzy multi-select editors for requested reviewers, assignees, labels,
-  and milestone. Support adding, removing, and clearing values with an explicit
-  before/after confirmation.
+- Add fuzzy editors for labels and milestone with an explicit before/after
+  confirmation.
 - Add top-level PR conversation replies and editing/deleting the viewer's own
   comments. Fetch and enforce per-comment update/delete permissions.
 - Add reaction add/remove actions while retaining the current read-only counts.