Refactor code and add tests

Change the function/class responsible for flattening objects.

demo.ts

@@ -1,14 +1,14 @@
 import { LocaleKit } from "./mod.ts";
 
 const locale = new LocaleKit({
-  languages: {
-    en: {
-      test: {
-        key: "Test Key",
-      },
-    },
-  },
-  fallback_language: "en",
+	languages: {
+		en: {
+			test: {
+				key: "Test Key",
+			},
+		},
+	},
+	fallback_language: "en",
 });
 
 console.log(locale.t("test.key"));

deno.json

@@ -1,23 +1,43 @@
 {
   "fmt": {
-    "exclude": ["README.md", "npm_build/"],
+    "exclude": [
+      "README.md",
+      "npm_build/"
+    ],
     "options": {}
   },
   "lint": {
-    "exclude": ["npm_build/"],
+    "exclude": [
+      "npm_build/"
+    ],
     "rules": {
-      "tags": ["recommended"],
+      "tags": [
+        "recommended"
+      ],
       "include": [],
       "exclude": []
     }
   },
   "test": {
-    "include": ["test/"],
-    "exclude": ["npm_build/"]
+    "include": [
+      "test/"
+    ],
+    "exclude": [
+      "npm_build/"
+    ]
   },
   "bench": {
-    "include": ["test/"],
-    "exclude": ["npm_build/"]
+    "include": [
+      "test/"
+    ],
+    "exclude": [
+      "npm_build/"
+    ]
   },
-  "compilerOptions": {}
-}
+  "compilerOptions": {},
+  "tasks": {
+    "lint": "deno run -A npm:@biomejs/biome lint **/*.ts",
+    "format": "deno run -A npm:@biomejs/biome format **/*.ts --write",
+    "check": "deno run -A npm:@biomejs/biome check --apply **/*.ts"
+  }
+}