24. fluid font size

Create a heading of fluid font size.

1. if viewport width is smaller than 200px, use 16px
2. if viewport width is bigger than 400px, use 32px
3. otherwise font-size is linearly scaled. For example if viewport is 300px = (200px + 400px) / 2, then font-size is 24px = (16px + 32px) / 2

<h1 class="title">BFE.dev</h1>