WPSeed 2.1.0 «Plug»

• Update to Gulp 4
• Restructuring
  • add structure.scss with contents from nav.scss (removed) and header/footer parts of content.scss
  • remove support for post-thumbnails (when using Gutenberg, this is obsolete on pages)
• Features/Updates
  • add .taplink for touch-device-only links
  • add browser-check/output
  • add function to check the current staging environment
  • add option to toggle font-preloading on/off
  • add css file for compatibility classes and browser-hacks
  • remove page-section from content css file
  • add custom css for the columns-block
  • add custom css for the downloads-block
  • only show navigation if the Main-Menu exists
  • add center/left/right aligns for default Gutenberg Button-Block
  • minor gulp update
• CleanUp
  • beautify php (thanks to @scherii)
  • remove obsolete function to allow SVG-uploads
  • rename Submenu to Footermenu
  • move general-containers to structure.scss
  • re-enable display of the admin bar (thanks to @Sigizmund2012)]))
• Bugfixes
  • add missing or wrong curly braces, classes and values (thanks to Hongwei Tang)
  • add missing curly braces (thanks to @Sigizmund2012)]))