add block feature

src-tauri/migrations/20230521092300_add_block_model.sql

@@ -0,0 +1,10 @@
+-- Add migration script here
+CREATE TABLE
+  blocks (
+    id INTEGER NOT NULL PRIMARY KEY,
+    account_id INTEGER NOT NULL,
+    kind INTEGER NOT NULL,
+    title TEXT NOT NULL,
+    content TEXT NOT NULL,
+    FOREIGN KEY (account_id) REFERENCES accounts (id)
+  );