title: Create discrete color bar with varying interval widths and no spacing between legend levels
body: <p>I'd like to reproduce this color scale in <code>ggplot2</code>:
  <a href="https://i.stack.imgur.com/B2k2Z.png" rel="noreferrer"><img src="https://i.stack.imgur.com/B2k2Z.png" alt="enter image description here"></a>
  (<a href="https://medium.com/@mbostock/command-line-cartography-part-1-897aa8f8ca2c" rel="noreferrer">Source</a>)</p>
  
  <p>In the past I have <a href="https://stackoverflow.com/questions/26802272/generating-a-color-legend-with-shifted-labels-using-ggplot2">found</a> that creating discrete color scales with labels in-between in <code>ggplot2</code> can be tricky.</p>
  
  <p>Can this be accomplished at all? A similar, but not completely identical question I have recently posed is <a href="https://stackoverflow.com/questions/50506696/steeper-gradients-in-scale-gradientn">this</a> one.</p>