[new feature] Add option to choose react-router

[StorytellerCZ]

I wrote an article about how to replace Flow Router with react-router in Mantra. It is pretty easy.

Given that Arunoda has left the community and his suggestion to use react-router anyway, I think we should provide the option of creating Mantra app with react-router like we do with Storybooks.

This will impact the creation of new project and modules (only core module will need router).

Thoughts?

[sungwoncho]

Sounds like an important feature. Some ideas:

mantra create --react-router to create a new app with react router and save router: react-router to mantra_cli.yaml.