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### Problem description
<!-- Describe the bug that you fixed/feature request that you
implemented, or link to an existing issue describing it -->
When starting ImHex on a MacBook model with both integrated and discrete
graphics, it will force the computer to use the discrete graphics card.
This causes increased power usage, meaning the fans will spin up, the
battery will drain faster, etc. This program is not very graphics
intensive, so using the discrete graphics card shouldn't be needed.
### Implementation description
<!-- Explain what you did to correct the problem -->
I changed the
[`GLFW_COCOA_GRAPHICS_SWITCHING`](https://www.glfw.org/docs/latest/window_guide.html#window_hints_osx)
setting in GLFW to not enforce using the discrete graphics.
### Screenshots
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make before/after sceenshots -->
### Additional things
<!-- Anything else you would like to say -->
My editor is configured to automatically remove trailing whitespace, so
I hope that those whitespace changes are ok
* Restyled macOS icon for Big Sur
* Update other icons
* Different gradients
* Reverted macOS icon because of design guidelines
* Final version of new icons
