Add EnTT to Engines and Frameworks

[skypjack]

Hello,

Before to create a PR I want to ask if it's worth it according to your goal.
EnTT started as a fast ECS in C++ a while ago and now is getting a general purpose framework for game development. Here is the link to the project.
At a first glance, it seems to me that it's good fit for the section mentioned in the title. What about?

Thanks.

[ellisonleao]

sure @skypjack ! feel free to open a PR to add it!