Fix WebImage empty placeholder

Fixes

• Revert the EmptyView usage when WebImage does not have placeholder, which fix iOS 13.3 .frame modifier issue on WebImage #73

Custom Manager

Features

• Add support to pass the .customManager context option to custom SDWebImageManager instance #71

Backward deployment and weak linking

Project

• Support backward deployment on iOS 12 with CocoaPods and Carthage #67
• Fix the CocoaPods issue on macCatalyst

Animated WebImage

Features

• Supports Native SwiftUI animated image, using SDAnimatedImagePlayer #65

Changes

• Drop WatchKit hack, now AnimatedImage does not support watchOS. #65

AnimatedImage State Fix

Fixes

• Fix the issue that AnimatedImage can not refresh their url/name/data after first initializer #62 #61

This is a important fix for all user who use AnimatedImage, upgrade as much as you can.

API documentation fix

Fixes

• Fix the placeholder API viewBuilder args to match the documentation #59

watchOS patch

Fixes

• Fix the issue that WatchKit patch will cause other WatchKit interfaceObject with sizing issue #56

WebImage improvement

Improvements

• Little improvement to WebImage to use EmptyView instead of EmptyImage when no placeholder available #49

watchOS AnimatedImage fix

Fixes

• Using the wrapper on watchOS AnimatedImage as well, try to solve the SwiftUI bug of aspectRatio #48
• Fix that the AnimatedImage's data or name initializer does not works, which affect version 0.8.0~0.8.1

Placeholder Image Convenience

Features

• Add the convenient method for WebImage to directly supply SwiftUI.Image for placeholder #47