be more explicit about requirements

This doesn't actually alter any of the requirements because activemodel
has activesupport as a dependency. We're being more explicit though.
This also fixes an issue where `bin/console` failed to load the core hash
extention `with_indifferent_access`.

active_interaction.gemspec

@@ -35,6 +35,7 @@ Gem::Specification.new do |gem| # rubocop:disable Metrics/BlockLength
  gem.test_files = Dir.glob(File.join('spec', '**', '*.rb'))
 
  gem.add_dependency 'activemodel', '>= 5', '< 7'
+ gem.add_dependency 'activesupport', '>= 5', '< 7'
 
  {
  'actionpack' => [],

lib/active_interaction.rb

@@ -1,6 +1,7 @@
 # frozen_string_literal: true
 
 require 'active_model'
+require 'active_support/core_ext/hash/indifferent_access'
 
 # Manage application specific business logic.
 #