tool: biome for formatting

package.json

@@ -7,6 +7,7 @@
 		"dev": "vite dev",
 		"build": "vite build",
 		"preview": "bun run build && wrangler dev",
+		"format": "biome check --write",
 		"prepare": "svelte-kit sync || echo ''",
 		"check": "svelte-kit sync && svelte-check --tsconfig ./tsconfig.json",
 		"check:watch": "svelte-kit sync && svelte-check --tsconfig ./tsconfig.json --watch",
@@ -14,6 +15,7 @@
 		"cf-typegen": "wrangler types ./src/worker-configuration.d.ts"
 	},
 	"devDependencies": {
+		"@biomejs/biome": "^2.3.14",
 		"@sveltejs/adapter-auto": "^7.0.0",
 		"@sveltejs/adapter-cloudflare": "^7.2.6",
 		"@sveltejs/kit": "^2.50.1",
@@ -26,4 +28,4 @@
 		"vite": "^7.3.1",
 		"wrangler": "^4.62.0"
 	}
-}
+}