add prettier config

.prettierrc.json

@@ -0,0 +1,14 @@
+{
+  "plugins": ["prettier-plugin-svelte"],
+  "overrides": [
+    {
+      "files": "*",
+      "excludeFiles": ["*.svelte", "*.html", "*.json"],
+      "options": {
+        "tabWidth": 4
+      }
+    },
+    { "files": "*.svelte", "options": { "parser": "svelte" } }
+  ],
+  "trailingComma": "es5"
+}

package.json

@@ -8,6 +8,9 @@
         "rollup"
       ]
     }
+  },
+  "devDependencies": {
+    "prettier": "^3.3.2",
+    "prettier-plugin-svelte": "^3.2.5"
   }
 }
-