Change suggestions for MLX42: docs and code

[552020]

1. We struggled a little bit understanding that the image is automatically updated by the library: was it just our incapacity to read the docs, or is it not explained good enough.

2. @552020 is highly unstatisfied with the naming of the variable pixel in the helper function of mlx_put_pixel. Cause that variable designes the channel of a pixel (the 8-bit section of a 32-bit pixel) and not the whole pixel.

          > It sounds like not being a virgin anymore
   

Yes, I add a PR in MLX42 already accepted! I spot a typo it's instead of its! 😀

The doc for MLX is quite light (maybe intentionnaly) but it is true that this seems to be an essential information

Just for me to be clear about it, we are talking about the fact that in MLX42 when you modify an image that you already put to the window the library already update the image in the window without the need of reputting it on the window, and this is the reason why the minimap (as a black background) was behind the walls. It would be anyway another issue than the one discussed in this issue.

Originally posted by @552020 in #152 (comment)