textproc/rubygem-action_text-trix: Add rubygem-action_text-trix 2.1.15

A Rich Text Editor for Everyday Writing

Compose beautifully formatted text in your web application. Trix is a WYSIWYG
editor for writing messages, comments, articles, and lists -- the simple
documents most web apps are made of. It features a sophisticated document model,
support for embedded attachments, and outputs terse and consistent HTML.

Trix is an open-source project from 37signals, the creators of Ruby on Rails.
Millions of people trust their text to us, and we built Trix to give them the
best possible editing experience. See Trix in action in Basecamp 3.