Introduce new esf::EventListener

[AndreasLrx]

Description

Introduce a new esf::EventListener in the esf::RenderWindow.

The listener is called when the RenderWindow.pollEvent is called, like in the esf::PollEvents system.

Example usage:

esf::RenderWindow &window =
    registry.addResource<esf::RenderWindow>(sf::VideoMode(1280, 720), "ECSTASY SFML integration: events");
window.setEventListener([&registry](const sf::Event &event) {
    std::cout << "Event " << event.type << std::endl;
    return false;
});
registry.addSystem<esf::PollEvents>();

What type of PR is this? (check all applicable)

• Refactor
• Feature
• Bug Fix
• Optimization
• Documentation Update

Added/updated tests?

• New tests written
• Existing tests updated
• Functionnal demo updated as a test
• Tests are not required because this is a documentation update
• I need help with writing tests

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Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 82.23%. Comparing base (e23abcc) to head (f42e78f).

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Additional details and impacted files

@@           Coverage Diff           @@
##             main     #160   +/-   ##
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  Coverage   82.23%   82.23%           
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  Files          64       64           
  Lines        1103     1103           
  Branches      353      353           
=======================================
  Hits          907      907           
  Misses        140      140           
  Partials       56       56           

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