title: Remove comma as thousands separator from quoted numbers in a CSV using sed
body: <p>My <code>sed</code> is pretty shaky, so I'm not sure how to take a row like this</p>
  
  <pre><code>1,2,"12,345",x,y,"a,b"
  </code></pre>
  
  <p>and turn it into</p>
  
  <pre><code>1,2,12345,x,y,"a,b"
  </code></pre>
  
  <p>So the number "12,345" becomes 12345, but "a,b" remains untouched.</p>
  
  <p>I would need to somehow preserve the values around the comma when the values are numeric. I have an idea how the regex would look like to only deal with digits, but not really sure how to just remove the comma, as opposed to removing the whole column.</p>