Add support for Apple Silicon

-Update classes to read correct Apple Silicon CPU sensor
-Update project to compile a Universal 2 binary. Upgraded Sparkle to 2.1.0 as that was the latest and supports ARM64.
-Add MacBookPro18,1 to Machines.plist

Sparkle.framework/Versions/B/Headers/SUAppcast.h

@@ -0,0 +1,44 @@
+//
+//  SUAppcast.h
+//  Sparkle
+//
+//  Created by Andy Matuschak on 3/12/06.
+//  Copyright 2006 Andy Matuschak. All rights reserved.
+//
+
+#ifndef SUAPPCAST_H
+#define SUAPPCAST_H
+
+#if __has_feature(modules)
+#if __has_warning("-Watimport-in-framework-header")
+#pragma clang diagnostic ignored "-Watimport-in-framework-header"
+#endif
+@import Foundation;
+#else
+#import <Foundation/Foundation.h>
+#endif
+#import <Sparkle/SUExport.h>
+
+NS_ASSUME_NONNULL_BEGIN
+
+@class SUAppcastItem;
+
+/**
+ The appcast representing a collection of `SUAppcastItem` items in the feed.
+ */
+SU_EXPORT @interface SUAppcast : NSObject
+
+- (instancetype)init NS_UNAVAILABLE;
+
+/**
+ The collection of update items.
+ 
+ These `SUAppcastItem` items are in the same order as specified in the appcast XML feed and are thus not sorted by version.
+ */
+@property (readonly, copy) NSArray<SUAppcastItem *> *items;
+
+@end
+
+NS_ASSUME_NONNULL_END
+
+#endif