SPM support

[raulriera]

Feature

It would be preferable to use Swift Package Manager over all the options disclosed in the readme file

[raulriera]

I was able to create a starting guide for this. But there appears to be issues with the inner submodule of .Client. Unable to trouble shoot because I can't get the SDK to compile with Carthage either

// swift-tools-version:5.3
// The swift-tools-version declares the minimum version of Swift required to build this package.

import PackageDescription

let package = Package(
	name: "FiskalySDK",
	defaultLocalization: "en",
	platforms: [
		.iOS(.v9)
	],
	products: [
		.library(
			name: "FiskalySDK",
			targets: ["FiskalySDK"]),
	],
	dependencies: [],
	targets: [
        .target(name: "FiskalySDK",
                path: "FiskalySDK"),
		.testTarget(name: "FiskalySDKTests",
					dependencies: ["FiskalySDK"],
                    path: "FiskalySDKTests"),
	]
)

[prempador]

Thank you @raulriera for the feature request. I will take a look into it as soon as I have time.

[havocked]

#35