Add ability to watch an episode

- Migration for new backing table.
- CRUD server functions, new components to display and interact.

sql/insert_viewing.sql

@@ -0,0 +1 @@
+insert into viewing (series_id, season, episode, "comment") values ($1, $2, $3, $4);

sql/select_viewings.sql

@@ -0,0 +1,3 @@
+select *
+from viewing
+where series_id = $1;