Fix: add passing viewed parameter (upbit#247)

Updated methods `illust_related()`, `illust_recommended()` in
`AppPixivAPI` class. Both of them have had `viewed` parameter in their
signatures but the parameter was unused.

pixivpy3/aapi.py

@@ -275,6 +275,8 @@ def illust_related(
             params["seed_illust_ids[]"] = [seed_illust_ids]
         elif isinstance(seed_illust_ids, list):
             params["seed_illust_ids[]"] = seed_illust_ids
+        if isinstance(viewed, list):
+            params["viewed[]"] = viewed
         r = self.no_auth_requests_call("GET", url, params=params, req_auth=req_auth)
         return self.parse_result(r)
 
@@ -315,6 +317,8 @@ def illust_recommended(
             params["include_ranking_illusts"] = self.format_bool(
                 include_ranking_illusts
             )
+        if isinstance(viewed, list):
+            params["viewed[]"] = viewed
 
         if not req_auth:
             if isinstance(bookmark_illust_ids, str):