Added test functionality for xCore build script

you can use the command line to test all the extensions with scripts/xcore test all
or you can test a single extension with scripts/score test <extension_name>
Multiline comments should be in the following format.
/**
  * My multi line comment,
  * should look like this.
*/

But your comments here are short enough to be on a single line.

Also write your sentences properly. Start the first letter with a capital and end with proper punctuation. Coding is a form of writing and you should write well!