custom plugin configuration for esbuild

[mhording]

Is your feature request related to a problem? Please describe.
We have a project with a custom webpack config now to iterate a lot of named fields and rename them in order for the names to be unique. This is a crucial part of our current build pipeline and works well with our current webpack setup. It would however be preferable if we could do the same trick using custom-esbuild and using a plugin like we are doing in our current setup.

It seems however the plugin support now is rather limited and the plugins are only able to do quite primitive job, like setting build versions. After a lot of googling I have come to the conclusion it is impossible at the moment to have the plugin do something more advanced since the onLoad event is already used some place earlier and that subsequent onLoad events in plugins are simply ignored.

Describe the solution you'd like
It would be great if the plugins could define their own onLoad events to more accurately support the features and pipeline in esbuild
as stated in for example https://esbuild.github.io/plugins/#on-load