Add support for multi-character sigils?

[gaggle]

FYI multi-character sigils don't work with this plugin. It thinks the code is malformed, and it results in the plugin considering the code invalid.

[gaggle]

E.g. this code is not considered valid by this plugin, but is valid Elixir:

  def sigil_DECIMAL(string, _modifiers) do
    Decimal.new(string)
  end

[joshuataylor]

Thanks for the code example, I'll see what's up.