message: Add alt tag to block images
diff: if block.has('image') && block.get('class') !== 'Media'
  .block-img
  a( href= block.getSourceUrl(), target='_blank', rel='nofollow' )
  - img( src= block.resizeImage(1000, 1000, 'large') )
  + img(
  + src= block.resizeImage(1000, 1000, 'large')
  + alt="#{block.get('description')}"
  + )
  if block.get('class') === 'Media'
  .block-media
  