title: Does a multi-value purrr::pluck exist?
body: <p>Seems like a basic question and perhaps I'm just missing something obvious ... but is there any way to <code>pluck</code> a sublist (with <code>purrr</code>)?
  More specifically, here's an initial list:</p>
  
  <pre><code>l &lt;- list(a = "foo", b = "bar", c = "baz")
  </code></pre>
  
  <p>And I want to return a new (sub-)list with only elements <code>a</code> and <code>b</code>.
  Normally, I'd just do 'base' R sub-listing:</p>
  
  <pre><code>l[c("a", "b")]
  </code></pre>
  
  <p>But this doesn't provide the nice <code>.default</code> handling of <code>pluck</code>.
  My understanding is that pluck 'replaces' <code>[[</code>, but is there a <code>purrr</code> equivalent for replacing <code>[</code>?</p>