title: Create Altair chart with grouped dates by week in X axis
body: <pre><code>DATE,AMOUNT
  2022-04-05,100
  2022-04-06,10
  2022-04-07,90
  2022-04-08,75
  2022-04-12,32
  2022-04-13,400
  2022-04-14,28
  2022-04-15,50
  </code></pre>
  <p>With a dataset like this, how can I create a bar chart grouped by week so the X axis shows only two bars, <code>april 03 - april 09</code> and <code>april 11 - april 17</code>? (Taking into account that the week starts on sundays, even tho there is no data for dates like <code>april 04</code>)</p>