Add documentation note for delegates being weakly referenced (#2802)

Author: zorgiepoo

Sparkle/SPUStandardUpdaterController.h

@@ -81,6 +81,8 @@ SU_EXPORT @interface SPUStandardUpdaterController : NSObject
  Create a new `SPUStandardUpdaterController` programmatically.
  
  The updater is started automatically. See `-startUpdater`  for more information.
+ 
+ Note the `updaterDelegate` and `userDriverDelegate` are weakly referenced, so you are responsible for keeping them alive.
  */
 - (instancetype)initWithUpdaterDelegate:(nullable id<SPUUpdaterDelegate>)updaterDelegate userDriverDelegate:(nullable id<SPUStandardUserDriverDelegate>)userDriverDelegate;
 
@@ -89,6 +91,8 @@ SU_EXPORT @interface SPUStandardUpdaterController : NSObject
  
  You can specify whether or not you want to start the updater immediately.
  If you do not start the updater, you must invoke `-startUpdater` at a later time to start it.
+ 
+ Note the `updaterDelegate` and `userDriverDelegate` are weakly referenced, so you are responsible for keeping them alive.
  */
 - (instancetype)initWithStartingUpdater:(BOOL)startUpdater updaterDelegate:(nullable id<SPUUpdaterDelegate>)updaterDelegate userDriverDelegate:(nullable id<SPUStandardUserDriverDelegate>)userDriverDelegate;
 

Sparkle/SPUStandardUserDriver.h

@@ -33,7 +33,7 @@ SU_EXPORT @interface SPUStandardUserDriver : NSObject <SPUUserDriver>
  Initializes a Sparkle's standard user driver for user update interactions
  
  @param hostBundle The target bundle of the host that is being updated.
- @param delegate The optional delegate to this user driver.
+ @param delegate The optional delegate to this user driver. Note the standard user driver weakly references the delegate, so you are responsible for keeping it alive.
  */
 - (instancetype)initWithHostBundle:(NSBundle *)hostBundle delegate:(nullable id<SPUStandardUserDriverDelegate>)delegate;
 

Sparkle/SPUUpdater.h

@@ -57,7 +57,7 @@ SU_EXPORT @interface SPUUpdater : NSObject
  @param hostBundle The bundle that should be targeted for updating.
  @param applicationBundle The application bundle that should be waited for termination and relaunched (unless overridden). Usually this can be the same as hostBundle. This may differ when updating a plug-in or other non-application bundle.
  @param userDriver The user driver that Sparkle uses for user update interaction.
- @param delegate The delegate for `SPUUpdater`.
+ @param delegate The delegate for `SPUUpdater`. Note the updater weakly references the delegate, so you are responsible for keeping it alive.
  */
 - (instancetype)initWithHostBundle:(NSBundle *)hostBundle applicationBundle:(NSBundle *)applicationBundle userDriver:(id <SPUUserDriver>)userDriver delegate:(nullable id<SPUUpdaterDelegate>)delegate;