message: fix: specify utf-8 encoding with meta tag
  We specify the encoding to be with a meta tag such that Electron
  won't get confused and try any other encodings.
  Change-Type: patch
  Changelog-Entry: Specify encoding with meta tag.
diff: <!DOCTYPE html>
  <html>
  <head>
  + <meta charset="UTF-8" />
  <title>Etcher</title>
  <link rel="stylesheet" type="text/css" href="../../node_modules/flexboxgrid/dist/flexboxgrid.css">
  <link rel="stylesheet" type="text/css" href="css/main.css">
  