Hi there, it seems you have the file for english as a default value i did downloaded and found the file with the language settings located on: summernote>src>js>summernote.js.
$.summernote = $.summernote || {};
  $.extend($.summernote, {
    version: '@VERSION',
    lang: {
      'en-US': {
        font: {
          bold: 'Bold',
          italic: 'Italic',
          underline: 'Underline',
          strike: 'Strike',
          clear: 'Remove Font Style',
          height: 'Line Height',
          size: 'Font Size'
        },
        image: {
          image: 'Picture',
          insert: 'Insert Image',
          resizeFull: 'Resize Full',
          resizeHalf: 'Resize Half',
          resizeQuarter: 'Resize Quarter',
          floatLeft: 'Float Left',
          floatRight: 'Float Right',
          floatNone: 'Float None',
          dragImageHere: 'Drag an image here',
          selectFromFiles: 'Select from files',
          url: 'Image URL'
        },
        link: {
          link: 'Link',
          insert: 'Insert Link',
          unlink: 'Unlink',
          edit: 'Edit',
          textToDisplay: 'Text to display',
          url: 'To what URL should this link go?'
        },
        video: {
          video: 'Video',
          videoLink: 'Video Link',
          insert: 'Insert Video',
          url: 'Video URL?',
          providers: '(YouTube, Vimeo, Vine, Instagram, or DailyMotion)'
        },
        table: {
          table: 'Table'
        },
        hr: {
          insert: 'Insert Horizontal Rule'
        },
        style: {
          style: 'Style',
          normal: 'Normal',
          blockquote: 'Quote',
          pre: 'Code',
          h1: 'Header 1',
          h2: 'Header 2',
          h3: 'Header 3',
          h4: 'Header 4',
          h5: 'Header 5',
          h6: 'Header 6'
        },
        lists: {
          unordered: 'Unordered list',
          ordered: 'Ordered list'
        },
        options: {
          help: 'Help',
          fullscreen: 'Full Screen',
          codeview: 'Code View'
        },
        paragraph: {
          paragraph: 'Paragraph',
          outdent: 'Outdent',
          indent: 'Indent',
          left: 'Align left',
          center: 'Align center',
          right: 'Align right',
          justify: 'Justify full'
        },
        color: {
          recent: 'Recent Color',
          more: 'More Color',
          background: 'BackColor',
          foreground: 'FontColor',
          transparent: 'Transparent',
          setTransparent: 'Set transparent',
          reset: 'Reset',
          resetToDefault: 'Reset to default'
        },
        shortcut: {
          shortcuts: 'Keyboard shortcuts',
          close: 'Close',
          textFormatting: 'Text formatting',
          action: 'Action',
          paragraphFormatting: 'Paragraph formatting',
          documentStyle: 'Document Style'
        },
        history: {
          undo: 'Undo',
          redo: 'Redo'
        }
      }
    }
  });Also, the css is there too, well for me this is a very strange plugin and have a few bugs on tags.... But  if it works for you good!
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