extend.plist

<plist>
<key>CFBundleDocumentTypes</key>
<array>
  <dict>
    <key>CFBundleTypeExtensions</key>
    <array>
      <string>png</string>
      <string>jpg</string>
      <string>jpeg</string>
      <string>svg</string>
    </array>
    <key>CFBundleTypeName</key>
    <string>png</string>
    <key>CFBundleTypeRole</key>
    <string>Editor</string>
    <key>CFBundleTypeIconFile</key>
    <string>Image Shrinker.icns</string>
  </dict>
</array>
</plist>