title: Regex: remove lines not starting with a digit
body: <p>I have been fighting this problem with the help of a RegEx cheat sheet, trying to figure out how to do this, but I give up... I have this lengthy file open in Notepad++ and would like to remove all lines that do not start with a digit (0..9). I would use the Find/Replace functionality of N++. I am only mentioning this as I am not sure what Regex implementation is N++ using... Thank you</p>
  
  <p>Example. From the following text:</p>
  
  <pre><code>1hello
  foo
  2world
  bar
  3!
  </code></pre>
  
  <p>I would like to extract</p>
  
  <pre><code>1hello
  2world
  3!
  </code></pre>
  
  <p>not:</p>
  
  <pre><code>1hello
  
  2world
  
  3!
  </code></pre>
  
  <p>by doing a find/replace on a regular expression.</p>