[Tracking]: Combine devmode and prodmode into ESM 2020

[devversion]

Notes:

• How will it work with ZoneJS if we target ES2020? custom transform?

[alan-agius4]

• How will it work with ZoneJS if we target ES2020? custom transform?

Or babel like we do in the Angular CLI.

[devversion]

Yeah, need to be careful though as this is super slow based in my recent testing. Potentially ESBuild could do the job?