Consider migrating time system to sf::Clock

[BlastWind]

In bin/main.cpp, we are using std::chrono to implement a fixed 60 frames per second game loop. SFML provides a sf::Clock module in handling this kind of stuff as well, perhaps use it instead?

https://www.sfml-dev.org/documentation/2.5.1/classsf_1_1Clock.php

[BlastWind]

Furthermore, Spritesheet.cpp uses sf::Clock as well, migrate this?

[aaronamk]

No

[BlastWind]

Haha, mean!

For those wondering why we chose not to: sf::Clock doesn't provide much extra abstraction, so, we are better off using the C++ standard library std to handle time. This way, if we were to for some reason migrate to another rendering library like SDL, we can still retain the time handling code.