Add visibility parameters to control scope of generated extension

Sources/ResgenSwift/Generate/Runnable/StringsConfiguration+Runnable.swift

@@ -10,6 +10,11 @@ import Foundation
 extension StringsConfiguration: Runnable {
 
     func run(projectDirectory: String, force: Bool) {
+        let args = getArguments(projectDirectory: projectDirectory, force: force)
+        Stringium.main(args)
+    }
+
+    func getArguments(projectDirectory: String, force: Bool) -> [String] {
         var args = [String]()
 
         if force {
@@ -23,18 +28,17 @@ extension StringsConfiguration: Runnable {
             "--langs",
             langs,
             "--default-lang",
-            defaultLang,
-            "--static-members",
-            "\(staticMembersOptions)",
-            "--xc-strings",
-            "\(xcStringsOptions)"
+            defaultLang
         ]
 
         // Add optional parameters
         [
             ("--extension-output-path", extensionOutputPath?.prependIfRelativePath(projectDirectory)),
             ("--extension-name", extensionName),
-            ("--extension-suffix", extensionSuffix)
+            ("--extension-suffix", extensionSuffix),
+            ("--visibility", visibility),
+            ("--xc-strings", staticMembers?.description),
+            ("--static-members", xcStrings?.description)
         ].forEach { argumentName, argumentValue in
             if let argumentValue {
                 args += [
@@ -44,6 +48,6 @@ extension StringsConfiguration: Runnable {
             }
         }
 
-        Stringium.main(args)
+        return args
     }
 }