chore(deps): update dependency textlint to v15

Author: renovate[bot]

package.json

@@ -29,7 +29,7 @@
   "devDependencies": {
     "docsify-cli": "^4.3.0",
     "husky": "^3.0.5",
-    "textlint": "^11.3.1",
+    "textlint": "^15.0.0",
     "textlint-filter-rule-whitelist": "^2.0.0",
     "textlint-rule-no-todo": "^2.0.1",
     "textlint-rule-preset-ja-spacing": "^2.0.1",