adds export (client and server sided) for GetCops

[Mustachedom]

Describe Pull request
added export for GetCops which returns the number of cops that are clocked in.

example: ( client and server side work the same way)

  if not exports['qb-policejob']:GetCops() >= Config.MinCops then 
       print('Not Enough Cops')
       return
 end

Or the latter

   if exports['qb-policejob']:GetCops() >= Config.MinCops then
       print('enough cops')
   end

Questions (please complete the following information):

• Have you personally loaded this code into an updated qbcore project and checked all it's functionality? [yes] (Be honest)
• Does your code fit the style guidelines? [yes]
• Does your PR fit the contribution guidelines? [yes]