sentry-5-esm-webpack-breaking-change

getsentry/sentry-javascript#1989

Steps

1. Run npm install or yarn
2. Run npm run build-and-check-es5 or yarn build-and-check-es5
3. Result: everything is OK, dist/main.jscontains ES5 code only
4. git checkout upgrade-to-sentry-5
5. Run npm run build-and-check-es5 or yarn build-and-check-es5
6. Result: dist/main.js contains ES6 code

ES-Check: there were 1 ES version matching errors.

          ES-Check Error:
          ----
          · erroring file: dist/main.js
          · error: SyntaxError: The keyword 'class' is reserved (125:0)
          · see the printed err.stack below for context
          ----

          SyntaxError: The keyword 'class' is reserved (125:0)