message: fix(site): broken line breaks
diff: <body>
  <h1>Package your kintone plug-in!</h1>
  <div id=input>
  - <p>Upload the zipped plug-in file.</ br>
  - A secret key file and a signed plug-in file will be generated.</ br>
  + <p>Upload the zipped plug-in file.<br>
  + A secret key file and a signed plug-in file will be generated.<br>
  The secret key will also need to be uploaded when repackaging your plug-in.</p>
  <ul>
  <li>Zip file: <input type=file class=contents></li>
  