fix(npm): fix main path

Author: azu

package.json

@@ -13,7 +13,7 @@
   },
   "version": "3.1.3",
   "description": "textlint rule for prh.",
-  "main": "lib/prh-rule.js",
+  "main": "lib/textlint-rule-prh.js",
   "files": [
     "lib",
     "src"