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/PrivateHeaders/SPUAppcastItemStateResolver.h

@@ -0,0 +1,37 @@
+//
+//  SPUAppcastItemStateResolver.h
+//  Sparkle
+//
+//  Created by Mayur Pawashe on 5/31/21.
+//  Copyright © 2021 Sparkle Project. All rights reserved.
+//
+
+#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 SUStandardVersionComparator, SPUAppcastItemState;
+@protocol SUVersionComparison;
+
+/**
+ Private exposed class used to resolve Appcast Item properties that rely on external factors such as a host.
+ This resolver is used for constructing appcast items.
+ */
+SU_EXPORT @interface SPUAppcastItemStateResolver : NSObject
+
+- (instancetype)init NS_UNAVAILABLE;
+
+- (instancetype)initWithHostVersion:(NSString *)hostVersion applicationVersionComparator:(id<SUVersionComparison>)applicationVersionComparator standardVersionComparator:(SUStandardVersionComparator *)standardVersionComparator;
+
+@end
+
+NS_ASSUME_NONNULL_END