Fix Incorrect Display Bounds Calculation for Linux

[Sohimaster]

This PR resolves an issue in the GetDisplayBounds function on Linux systems where:

    1. Bounds were incorrectly calculated due to improper handling of absolute coordinates.
    2. Displays with non-standard arrangements produced incorrect bounds.

Changes:

    1. Updated GetDisplayBounds to use absolute coordinates based on xinerama data.

Testing:

    1. Verified the fix using multi-monitor setups on Linux.
    2. Confirmed screenshots correctly match individual monitor bounds.

[Sohimaster]

@kbinani Hi! Let's merge the fix if you don't have any questions

[kbinani]

@Sohimaster Thanks for the PR. According to the coordinate section in the README, this library treats the top-left of the primary screen as the origin. Your changes seem to break that design. Please review the README’s coordinate section to ensure consistency with our approach.

[Sohimaster]

@kbinani not really sure what it means but the library wasn't working for me before as it doesn't expect the primary screen to have index different than 0 (as in my setup in the picture)

so when I was taking a screenshot of my primary screen, it would capture the other one instead with an incorrect resolution. As for the other one, it did not capture anything at all. So I did some debugging and found the cause which I fixed in this PR