Investigate if we can reduce translations file size in JS

[ferblape]

@Crashillo has been investigating a bit how to reduce the size of the JS packs by reducing the translations file:

• check the namespaces in ignore-missing and ignore-unused. These options were filled with keys used in JS because Ruby wasn't able to detect them. It seems that it has been improved and we can check again

• investigate if we can skip English translations when dumping the JS file

[Crashillo]

Checking its docs I'm seeing really interesting things, as:

Create multiple files by language:

translations:
- file: 'public/javascripts/en.js'
  only: 'en.*'
- file: 'public/javascripts/pt-BR.js'
  only: 'pt-BR.*'

Use loops in the config file:

translations:
<% Widgets.each do |widget| %>
- file: <%= "'#{widget.file}'" %>
  only: <%= "'#{widget.only}'" %>
<% end %>

We might split translations into files such as:

es.gobierto_MODULE.js
ca.gobierto_MODULE.js
es.gobierto_common.js
...

In such a way that the import would bring only the current locale files

[Crashillo]

I removed the import for a packs, and I noticed the following:

The texts keep working as they're coming from backend, so:
Does it worth ONLY generate those which are required in javascript? Append a namespace for them (like js.gobierto_....) and creates a very much simpler files.