Access configuration flag in custom-esbuild plugin

[RaulPROP]

Is your feature request related to a problem? Please describe.
This is a feature request.

Describe the solution you'd like
I'd love to be able to access the configuration string (like in custom-webpack with the targetOptions.configuration) in the esbuild plugins and indexHtmlTransformer (i.e.: the --configuration flag).

Describe alternatives you've considered
The only alternative that I see is overriding the plugins and indexHtmlTransformer for each configuration (i.e.: having a plugin-development.ts, plugin-production.ts, etc).

Additional context
I guess this is related to #1661 in some way.