Integrate with Swift Package Index (#684)

.spi.yml

@@ -0,0 +1,8 @@
+---
+version: 1
+builder:
+  configs:
+    - platform: ios
+      documentation_targets: [
+        Analytics, Circumspect, Core, CoreBusiness, Player
+      ]

README.md

@@ -3,7 +3,7 @@
 
 # Overview
 
-[![GitHub releases](https://img.shields.io/github/v/release/SRGSSR/pillarbox-apple)](https://github.com/SRGSSR/pillarbox-apple/releases) [![platform](https://img.shields.io/badge/platfom-ios%20%7C%20tvos-blue)](https://github.com/SRGSSR/pillarbox-apple) [![SPM compatible](https://img.shields.io/badge/SPM-compatible-4BC51D.svg?style=flat)](https://swift.org/package-manager) [![GitHub license](https://img.shields.io/github/license/SRGSSR/pillarbox-apple)](../LICENSE)
+[![Releases](https://img.shields.io/endpoint?url=https%3A%2F%2Fswiftpackageindex.com%2Fapi%2Fpackages%2FSRGSSR%2Fpillarbox-apple%2Fbadge%3Ftype%3Dswift-versions)](https://swiftpackageindex.com/SRGSSR/pillarbox-apple) [![Platforms](https://img.shields.io/endpoint?url=https%3A%2F%2Fswiftpackageindex.com%2Fapi%2Fpackages%2FSRGSSR%2Fpillarbox-apple%2Fbadge%3Ftype%3Dplatforms)](https://swiftpackageindex.com/SRGSSR/pillarbox-apple) [![SPM compatible](https://img.shields.io/badge/SPM-compatible-4BC51D.svg?style=flat)](https://swift.org/package-manager) [![GitHub license](https://img.shields.io/github/license/SRGSSR/pillarbox-apple)](LICENSE)
 
 Pillarbox is the iOS and tvOS modern reactive SRG SSR player ecosystem implemented on top of AVFoundation and AVKit. Pillarbox has been designed with robustness, efficiency and flexibilty in mind, with full customization of: