title: regex to match only one capital letter
body: <p>I'm trying to match characters but I need to only match single capital letters.
  For example:</p>
  
  <pre><code>'Hello World' - 2 matches
  'Hello WOrld' - 1 match
  'HEllo WOrld' - 0 matches
  </code></pre>
  
  <p>So far I have <code>/(?![A-Z]{1})/g</code> but I think I've misinterpreted what a negative lookahead is.</p>
  
  <p>Thanks!</p>