title: Merging two yaml documents while concatenating arrays
body: <p>I want to merge two yaml documents with the result containing</p>
  <ul>
  <li>all mapped values (with the last one taking precedence)</li>
  <li>concatenated arrays</li>
  </ul>
  <p>e.g. given this file</p>
  <pre><code># file1.yml
  animals:
    - elephant
      donkey
  flavours:
    sour:
      - lemon
    sweet:
      - chocolate
  strange: true
  </code></pre>
  <p>and this file</p>
  <pre><code>#file2.yml
  animals:
    - monkey
      pelican
  flavours:
    sweet:
      - vanilla
  strange: false
  </code></pre>
  <p>the result should contain all the nodes, with merged arrays and values that are not arrays from the last file</p>
  <pre><code>#result.yml
  animals:
    - elephant
      donkey
      monkey
      pelican
  flavours:
    sour:
      - lemon
    sweet:
      - chocolate
        vanilla
  strange: false
  </code></pre>
  <p>Can yq do this, maybe?</p>