feat: add swift from go

swift-from-go/Sources/go-swift/go_swift.swift

@@ -0,0 +1,7 @@
+@_cdecl("sayHello") // export to C as `sayHello``
+public func sayHello(namePtr: UnsafePointer<CChar>?) {    
+    // Creates a new string by copying the null-terminated UTF-8 data (C String) 
+    // referenced by the given pointer.
+    let name = String(cString: namePtr!)
+    print("Welcome, \(name)!")
+}