title: all combinations of items in a list. all containing alle items
body: <p>looking for an easy way to get all combinations
  input: list of strings</p>
  
  <pre><code>list = ["a", "b", "c", "d"]
  </code></pre>
  
  <p>output: nested list of strings</p>
  
  <pre><code>[["abcd"],["abc", "d"],["ab","cd"],["a","bcd"],["ab","c","d"],["a","bc","d"],["a","b","cd"],["a","b","c","d"]]
  </code></pre>