Implemented the Outdated subcommand (#6)

This PR contains the work done to implement the `Outdated` subcommand that check for outdated package dependencies in a *Hummingbird* project.

Reviewed-on: #6
Co-authored-by: Javier Cicchelli <javier@rock-n-code.com>
Co-committed-by: Javier Cicchelli <javier@rock-n-code.com>

Executable/Sources/Options/OutdatedOptions.swift

@@ -0,0 +1,13 @@
+import ArgumentParser
+import ColibriLibrary
+
+extension Colibri.Outdated {
+    struct Options: ParsableArguments, Locationable {
+        
+        // MARK: Properties
+        
+        @Option(name: .shortAndLong)
+        var location: String?
+        
+    }
+}