chore: init sample folder

sample/Migra.toml

@@ -0,0 +1,4 @@
+directory = "database"
+
+[database]
+connection = "postgres://postgres:123456@localhost:5434/migra"

sample/database/schema.sql

@@ -0,0 +1,6 @@
+
+create table tags (
+    id          serial          primary key,
+    name        text            not null unique check(length(name) > 0),
+    created_at  timestamp       not null default current_timestamp
+);