fix: add type declaration for ./style export to resolve TS2882 error

The ./style export only pointed to a CSS file without type definitions,
causing tsc to fail with TS2882 when projects import inklayer-react/style.
Added dist/style.d.ts with explicit module declaration and updated package.json
exports to include types field.

Author: Laomai-codefee

dist/style.d.ts

@@ -0,0 +1 @@
+export {}

package.json

@@ -42,7 +42,10 @@
             "import": "./dist/index.es.js",
             "require": "./dist/index.cjs.js"
         },
-        "./style": "./dist/inklayer-react.css"
+        "./style": {
+            "types": "./dist/style.d.ts",
+            "default": "./dist/inklayer-react.css"
+        }
     },
     "sideEffects": [
         "*.css",