Replace sf::Uint8 with std::uint8_t

[pifopi]

Hello !

Just a small update because sfml recently replaced sf::Uint8 with std::uint8_t
SFML/SFML@e2528de

The CI fails with mingw errors but it is not linked to my change (only submitting an empty CL to trigger the CI leads to the exact same issue).

Thanks a lot for your work !

[ChrisThrasher]

You can thank me for this new massive API break :) For the record this is a change in the in-development major update to SFML, not in the 2.x series. If we still want to support both SFML 2 and 3 without separate branches and we're okay with using C++11, we can safely switch to the standard fixed width aliases which SFML 3 is already using.

[eliasdaler]

Just to be clear - this change still works with SFML 2.5, right?
(also mingw CI is failing for some reason not related to this PR, I don't have time to fix it right now, unfortunately)

[ChrisThrasher]

Just to be clear - this change still works with SFML 2.5, right?

I think so? I'm not sure how it would break.

[oprypin]

I mean, it could be slightly painful if these types appeared anywhere at the boundary of the API of imgui-sfml, but they don't. Yeah it's safe. And CI passes too, so of course it has to be fine.

[pifopi]

Yes, it's fine with SFML 2.5 ^^

[eliasdaler]

Okay, thanks, everyone! Merged.