Battery: move detection code into src/detection

Prepare for macOS implementation

src/detection/battery/battery_android.c

@@ -0,0 +1,10 @@
+#include "fastfetch.h"
+#include "common/io.h"
+#include "battery.h"
+
+#include <dirent.h>
+
+const char* ffDetectBatteryImpl(FFinstance* instance, FFlist* results) {
+    FF_UNUSED(instance, results)
+    return "Unimplemented";
+}