feat: expose Transformer

[lpatiny]

@targos I have again the problem of the build that does not contain Transformer.

I have installed the last version of 'GWT' and I'm using the last version of actelion java code. Is this correct ? My config file is:

{
  "gwt": "/Users/lpatiny/gwt/gwt-2.10.0",
  "openchemlib": "/Users/lpatiny/git/actelion/openchemlib/src"
}

Trying to compile npm run build-debug-full I get 442 errors in the log file like:

   Tracing compile failure path for type 'com.actelion.research.util.datamodel.IntArray'
      Errors in 'file:/Users/lpatiny/git/cheminfo/openchemlib-js/src/com/actelion/research/gwt/chemlib/com/actelion/research/util/datamodel/IntArray.java'
         Line 458: No source code is available for type java.util.StringTokenizer; did you forget to inherit a required module?
      Checked 1 dependencies for errors.
   Tracing compile failure path for type 'com.google.gwt.validation.client.impl.GwtValidationContext'
      Errors in 'com/google/gwt/validation/client/impl/GwtValidationContext.java'
         Line 25: The import javax.validation.metadata cannot be resolved
         Line 116: TraversableResolver cannot be resolved to a type
         Line 136: ConstraintDescriptor cannot be resolved to a type
         Line 70: TraversableResolver cannot be resolved to a type

[targos]

You have to look for [ERROR] in the logs (not sure about the syntax, but it contains the brackets). Many errors are not problematic (because the code is not used in the end)

[targos]

You can also search for the name of the class that you add/modify.

In this case, here is the relevant error:

   Tracing compile failure path for type 'com.actelion.research.gwt.core.JSTransformer'
      Errors in 'file:/home/runner/work/openchemlib-js/openchemlib-js/src/com/actelion/research/gwt/core/JSTransformer.java'
         Line 7: JsType cannot be resolved to a type
      Checked 1 dependencies for errors.

It's just missing an import for the JsType decorator. In other files we do import jsinterop.annotations.*;