See this

p span:before {
    animation: dots 2s linear infinite;
    content: '';   
}

  @keyframes dots {
    0%, 20% {
      content: '.';
    }
    40% {
      content: '..';
    }
    60% {
      content: '...';
    }
    90%, 100% {
      content: '';
    } 
}