✨ init bs.gui

[theogiraudet]

Tasks to do before merging

• I accept to publish my contribution under MPL v2 License
• My pull request is linked to an existing issue
• I have added my contribution to the changelog
• If my pull request is a new or modify an existing feature:
  • I have documented my contribution (/docs)
  • I have added or updated the header of the features' root function I contribute
  • I have tested my contribution

[theogiraudet]

Close #193

[theogiraudet]

@aksiome The code is not really up to date, but you can check the beginning of the documentation about the interaction API, if you have some feedback.
As you will see, there currently are three APIs in this module.
To discuss.

[theogiraudet]

Two things about the documentation:

• I think the term "listener" is not useful anymore, we can replace it by "interaction entity".
• Should we document the default callback?
  Finally, the module is not documented in the changelog.