Was going through _document and noticed some variable shadowing going on. Added a rule for it to our eslint configuration and went through all warnings with @Timer.
* Add custom profiler / tracer
This captures both client/production builds and everything before and after is cpu profiled, which makes sure that the whole process instead of just webpack is included in the final report.
* Update tests
* Update profiling-plugin.js
* Rename profiling-plugin.js to profiling-plugin.ts
* Update profiling-plugin.ts
* Update and rename profiling-plugin.ts to profiling-plugin.js
* Update webpack-config.ts
* Update profiling-plugin.js
* Add types
* Add missing type
* Add back TypeScript linting
* Remove tracing-js
