message: add word unit test debug config
diff: // For more information, visit: https://go.microsoft.com/fwlink/?linkid=830387
  "version": "0.2.0",
  "configurations": [
  + {
  + "name": "WU",
  + "type": "node",
  + "request": "launch",
  + "sourceMaps": true,
  + "protocol": "inspector",
  + "program": "${workspaceRoot}/dist/merge-tree/wordUnitTests.js"
  + },
  {
  "name": "TestFarm",
  "type": "node",
  