message: Add filenames to package.json
  Summary:
  Add filenames to package.json, so that they can be recognized as Starlark file.
  NOTE: Besides 'BUCK', 'BUILD_DEFS', 'DEFS', 'TARGETS', I also added 'BUILD', 'WORKSPACE'
  to the filenames, since they seem useful.
diff: ".sky",
  ".bzl"
  ],
  + "filenames": [
  + "BUILD",
  + "WORKSPACE",
  + "BUCK",
  + "BUILD_DEFS",
  + "DEFS",
  + "TARGETS"
  + ],
  "configuration": "./syntaxes/starlark.configuration.json"
  }
  ],
  