chore(npm): add "textlintrule" as keywords
chore(npm): add "textlintrule" as keywords

https://github.com/textlint/textlint/issues/253

textlint-ja/textlint-rule-no-dropping-the-ra,azu/textlint-rule-no-dropping-the-ra,textlint-ja/textlint-rule-no-dropping-the-ra