Add Swift API for TTS (#439)

swift-api-examples/tts.swift

@@ -0,0 +1,31 @@
+func run() {
+  let model = "./vits-vctk/vits-vctk.onnx"
+  let lexicon = "./vits-vctk/lexicon.txt"
+  let tokens = "./vits-vctk/tokens.txt"
+  let vits = sherpaOnnxOfflineTtsVitsModelConfig(
+    model: model,
+    lexicon: lexicon,
+    tokens: tokens
+  )
+  let modelConfig = sherpaOnnxOfflineTtsModelConfig(vits: vits)
+  var ttsConfig = sherpaOnnxOfflineTtsConfig(model: modelConfig)
+
+  let tts = SherpaOnnxOfflineTtsWrapper(config: &ttsConfig)
+
+  let text = "How are you doing? Fantastic!"
+  let sid = 99
+  let speed: Float = 1.0
+
+  let audio = tts.generate(text: text, sid: sid, speed: speed)
+  let filename = "test.wav"
+  audio.save(filename: filename)
+
+  print("\nSaved to:\n\(filename)")
+}
+
+@main
+struct App {
+  static func main() {
+    run()
+  }
+}