title: How do I use "custom filter" prop in data tables in vuetify? or How do I create a custom filter to filter by headers?
body: <p>As of date of posting, I cannot find any documentation to use the "custom filter" prop in data tables.</p>
  
  <p>I just want to create a custom filter to filter my data table by headers.
  I have a dropdown, and when user click on one of the options for the dropdown, it will filter the list for one specific header.</p>
  
  <p>Example:
  Dropdown options: 
  Food type: fruit, meat, vegetable</p>
  
  <ol>
  <li>Bakchoi       (vegetable)</li>
  <li>Pork          (meat)</li>
  <li>Chicken Thigh (meat)</li>
  <li>watermelon    (fruit)</li>
  </ol>
  
  <p>If I select dropdown as meat, it should only show me pork and chicken thigh.</p>