Fixed typo on , added new Feature class to replace the deprecated

[g-kanoufi]

Description of the Change

• Removal of a typo on includes/functions/core.php on line 17. A trailing '/' was provoking a fatal error at activation.
• Addition of a new class file class-ep-stream-feature.php in includes/classes to register the Stream feature and removing the call to the deprecated ep_register_feature

Closes #6 possibly

How to test the Change

Deactivate and re-activate the plugin and see that it works as expected :)

Changelog Entry

Added - New Stream Feature Class extending the ElasticPress/Feature class Removed - use of the deprecated ep_register_feature function Fixed - Typo in includes/functions/core.php

Checklist:

• [x] I agree to follow this project's Code of Conduct.
• [ ] I have updated the documentation accordingly.
• [ ] I have added tests to cover my change.
• [ ] All new and existing tests pass.

[g-kanoufi]

Hi guys, sorry took me a long time to push the changes. Just so you guys know, this PR is actually only making the plugin activating without error. But i don't think it's indexing stream at all.

Happy to help if you guide me a bit on this :)