support for target.js in pxt serve
support for target.js in pxt serve

Microsoft/pxt,switch-education/pxt,playi/pxt,Microsoft/pxt,switch-education/pxt,switchinnovations/pxt,switch-education/pxt,Microsoft/pxt,switch-education/pxt,playi/pxt,playi/pxt,switchinnovations/pxt,playi/pxt,switchinnovations/pxt,switch-education/pxt,Microsoft/pxt,Microsoft/pxt,switchinnovations/pxt