title: Show extra columns when hovering in a scatter plot with hvplot
body: <p>I'm trying to add a label or hover column to the points in a scatter plot, but to no avail.</p>
  
  <p>For use as example data:</p>
  
  <pre class="lang-py prettyprint-override"><code>import pandas as pd
  import holoviews as hv
  import hvplot.pandas
  
  df = pd.read_csv('http://assets.holoviews.org/macro.csv', '\t')
  
  df.query("year == 1966").hvplot.scatter(x="gdp", y="unem")
  </code></pre>
  
  <p>results in the picture below. If I hover over this item I cannot see, which country is represented by the dot (which makes it rather useless). I could use the additional keyword <code>color="country"</code>in the scatterplot call. This would lead to an additional legend (which could be turned off) and the value country: countryname is added to the hover field.</p>
  
  <p><a href="https://i.stack.imgur.com/Wycct.png" rel="noreferrer"><img src="https://i.stack.imgur.com/Wycct.png" alt="Scatter plot gdp vs. unemployment, country indicator is missing"></a></p>
  
  <p>Is there an option that just adds the column to my hover without adding a legend and changing the color?</p>