message: Update typescript target/lib to ES2019
  This way we don't get async/await compiled to an ugly state machine, which means a slightly nicer debug experience.
diff: {
  "compilerOptions": {
  + "lib": [
  + "ES2019"
  + ],
  "module": "commonjs",
  - "target": "es6",
  + "target": "ES2019",
  "outDir": "out",
  "noImplicitReturns": true,
  "noUnusedLocals": false,
  "noUnusedParameters": false,
  "suppressImplicitAnyIndexErrors": true,
  - "lib": [
  - "es6"
  - ],
  "sourceMap": true,
  "strictNullChecks": true,
  "experimentalDecorators": true,
  