#25534 - Add license and platform to the gemspec

This pull requests adds the missing MIT license to the gemspec.  While adding the license it was discovered that the platform wasn't declared so that was added as well.

[#25534](https://squaremouth.lighthouseapp.com/projects/63460-viper/tickets/25534-add-the-mit-license-to-the-has_breadcrumb-gem)