Add missing i18n to native macOS receiver selector and refactor

app/NativeMacReceiverSelector/util.swift

@@ -0,0 +1,19 @@
+import Cocoa
+
+func makeLabel(_ text: String,
+               size: CGFloat = 0,
+               color: NSColor = NSColor.textColor) -> NSTextField {
+
+    let textField = NSTextField()
+    textField.stringValue = text
+    textField.backgroundColor = .clear
+    textField.isEditable = false
+    textField.isBezeled = false
+    textField.sizeToFit()
+
+    // Text
+    textField.font = NSFont.systemFont(ofSize: size)
+    textField.textColor = color
+
+    return textField
+}