Adds migrations for new models

internal/database/migrations/3_article.sql

@@ -0,0 +1,13 @@
+-- +migrate Up
+CREATE table article (
+  id INTEGER PRIMARY KEY,
+  name text NOT NULL,
+  url text NOT NULL UNIQUE,
+  read INTEGER DEFAULT 0,
+  readAt text,
+  feedId INTEGER,
+  FOREIGN KEY (feedId) REFERENCES feed(id)
+);
+
+-- +migrate Down
+DROP TABLE article;