Support for transpiling .js files (#9160)

* Remove some `.es6` from comments where it does not matter

* Use a post processor for transpilation

This will allow us to eventually use the directory structure to
transpile rather than the extension.

* FIX: Some errors and clean up in confirm-new-email

It would throw an error if the webauthn element wasn't present.
Also I changed things so that no-module is not explicitly
referenced.

* Remove `no-module`

Instead we allow a magic comment: `// discourse-skip-module` to prevent
the asset pipeline from creating a module.

* DEV: Enable babel transpilation based on directory

If it's in `app/assets/javascripts/dicourse` it will be transpiled
even without the `.es6` extension.

* REFACTOR: Remove Tilt/ES6ModuleTranspiler

lib/freedom_patches/raw_handlebars.rb

@@ -12,8 +12,8 @@ class Barber::Precompiler
     if !@precompiler
 
       source = File.read("#{Rails.root}/app/assets/javascripts/discourse-common/lib/raw-handlebars.js.es6")
-      template = Tilt::ES6ModuleTranspilerTemplate.new {}
-      transpiled = template.babel_transpile(source)
+      transpiler = DiscourseJsProcessor::Transpiler.new(skip_module: true)
+      transpiled = transpiler.perform(source)
 
       # very hacky but lets us use ES6. I'm ashamed of this code -RW
       transpiled = transpiled[0...transpiled.index('export ')]