Brightness: add new module (macOS)

It turns out that merging brightness module into resolution module is a bad idea.

src/detection/brightness/brightness.h

@@ -0,0 +1,17 @@
+#pragma once
+
+#ifndef FF_INCLUDED_detection_brightness_brightness
+#define FF_INCLUDED_detection_brightness_brightness
+
+#include "fastfetch.h"
+#include "util/FFlist.h"
+
+typedef struct FFBrightnessResult
+{
+    FFstrbuf name;
+    float value;
+} FFBrightnessResult;
+
+const char* ffDetectBrightness(FFlist* result); // list of FFBrightnessResult
+
+#endif

src/detection/brightness/brightness_apple.c

@@ -0,0 +1,33 @@
+#include "brightness.h"
+
+#include <CoreGraphics/CoreGraphics.h>
+
+extern int DisplayServicesGetBrightness(CGDirectDisplayID display, float *brightness) __attribute__((weak_import));
+
+const char* ffDetectBrightness(FFlist* result)
+{
+    if(DisplayServicesGetBrightness == NULL)
+        return "DisplayServices function DisplayServicesGetBrightness is not available";
+
+    CGDirectDisplayID screens[128];
+    uint32_t screenCount;
+    if(CGGetOnlineDisplayList(sizeof(screens) / sizeof(screens[0]), screens, &screenCount) != kCGErrorSuccess)
+        return "CGGetOnlineDisplayList() failed";
+
+    for(uint32_t i = 0; i < screenCount; i++)
+    {
+        CGDirectDisplayID screen = screens[i];
+        float brightness;
+        if(DisplayServicesGetBrightness(screen, &brightness) != kCGErrorSuccess)
+            continue;
+
+        FFBrightnessResult* display = (FFBrightnessResult*) ffListAdd(result);
+        if(CGDisplayIsBuiltin(screen))
+            ffStrbufInitS(&display->name, "built-in");
+        else
+            ffStrbufInitF(&display->name, "external-%u", (unsigned) screen);
+        display->value = brightness * 100;
+    }
+
+    return NULL;
+}

src/detection/brightness/brightness_nosupport.c

@@ -0,0 +1,6 @@
+#include "brightness.h"
+
+const char* ffDetectBrightness(FF_UNUSED_PARAM FFlist* result)
+{
+    return "Not supported on this platform";
+}