Add some Java code snippets

We can add a bunch of java code snippet, to make vs code more productive:

  • syserr -> System.err.println()
  • sysout -> System.out.println()
  • if, if/else, if not null, if null
  • try catch block
  • static main method
  • enhanced for loop
  • private/protected/public methods

and probably also a bunch of others