message: docs: Use a shield image instead of a svg image
diff: # create-kintone-plugin
  [![npm version](https://badge.fury.io/js/%40koba04%2Fcreate-kintone-plugin.svg)](https://badge.fury.io/js/%40koba04%2Fcreate-kintone-plugin)
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  A CLI tool for creating a kintone plugin!
  