ID23. No minimal character for suggestions

[paarals]

Currently, suggestion have validations on the minimum and maximum amount of characters allowed that are hardcoded:
https://github.com/openpoke/decidim-module-participatory-documents/blob/78d146304430b08574e78d58d69d684abfc2d630/app/forms/decidim/participatory_documents/suggestion_form.rb#L9

We need to make it configurable at the module configuration level and also at the component level, something like the number of chars allowed in the comments for the proposals component:

module Decidim
  # This namespace holds the logic of the `decidim-participatory_documents` module.
  module ParticipatoryDocuments
    include ActiveSupport::Configurable

    # ..desc
    config_accessor :min_suggestion_length do
      5
    end
...
  end
end

Tasks:

• Add global configuration option for minimal/maximum suggestion length. Defaults are 5/500
• Add component configuration for minimal/maximum suggestion length. Defaults to the configured in the module.
• Add a readme description of the option (or at least a todo)
• Specs

[paarals]

awesome must limited also suggestions characters (like letterbox)