⚡ improvement(build): suppress rollup deprecated warning

NOTE:
ezolenko/rollup-plugin-typescript2#126

Author: kazupon

package.json

@@ -18,7 +18,7 @@
     "rollup-plugin-commonjs": "^9.2.0",
     "rollup-plugin-node-resolve": "^4.0.0",
     "rollup-plugin-replace": "^2.1.0",
-    "rollup-plugin-typescript2": "^0.18.1",
+    "rollup-plugin-typescript2": "^0.19.2",
     "uglify-js": "^2.7.5",
     "vuepress": "^1.0.0-alpha.31"
   },