title: Laravel Validation for integers or specific word
body: <p>I'm creating a validation rule where <code>location</code> attribute can have any <code>integer</code> or a word <code>"all"</code> value.
  <br>
  For integer validation I use this rule: <pre>'location' => 'required|integer'</pre> and for a particular word I can use this rule:</p>
  
  <pre>'location' => ['required', Rule::in([all])] </pre>
  
  <p>How can apply both of rules together so that <code>location</code> can either be any integer or the word <code>"all"</code>?
  Can regex be of any help here?</p>