Package target setup (#1)

This PR contains the work done to setup the *executable*, *library*, and *test* targets for the Swift package. In addition, some boilerplate code has been removed.

Reviewed-on: #1
Co-authored-by: Javier Cicchelli <javier@rock-n-code.com>
Co-committed-by: Javier Cicchelli <javier@rock-n-code.com>

Sources/Executable/Colibri.swift

@@ -0,0 +1,13 @@
+import ArgumentParser
+import ColibriLibrary
+
+@main
+struct Colibri: AsyncParsableCommand {
+    
+    // MARK: Functions
+    
+    func run() async throws {
+        // ...
+    }
+    
+}