Override UnityUI Text class to add a justify option
Import TextJustified.cs and Editor/TextJustifiedEditor.cs in your project.
Simply add TextJustified.cs on your UI object instead of the Text component. Use it the same way as the UnityUI Text component, only a checkbox for justification is added.
It's kind of a quick fix. I did not test it extensively and is totally not optimized. I recommend testing before using it in a serious project.