v2.11.0 of pdfx

Flutter plugin to render & show PDF pages as images on Web, MacOS, Windows, Android and iOS. Changelog excerpt: - Added Swift Package Manager support for iOS and macOS, consolidating the duplicated Apple implementation into shared Darwin sources while retaining CocoaPods compatibility [pull#623](https://github.com/ScerIO/packages.flutter/pull/623) - Fixed a NaN/Infinity crash in…