examples : add README.md to tts example [no ci] (ggml-org#11155)

* examples : add README.md to tts example [no ci]

* squash! examples : add README.md to tts example [no ci]

Fix heading to be consistent with other examples, and add a quickstart
section to README.md.

* squash! examples : add README.md to tts example [no ci]

Fix spelling mistake.

Author: danbev

examples/tts/README.md

@@ -0,0 +1,80 @@
+# llama.cpp/example/tts
+This example demonstrates the Text To Speech feature. It uses a
+[model](https://www.outeai.com/blog/outetts-0.2-500m) from
+[outeai](https://www.outeai.com/).
+
+## Quickstart
+If you have built llama.cpp with `-DLLAMA_CURL=ON` you can simply run the
+following command and the required models will be downloaded automatically:
+```console
+$ build/bin/llama-tts --tts-oute-default -p "Hello world" && aplay output.wav
+```
+For details about the models and how to convert them to the required format
+see the following sections.
+
+### Model conversion
+Checkout or download the model that contains the LLM model:
+```console
+$ pushd models
+$ git clone --branch main --single-branch --depth 1 https://huggingface.co/OuteAI/OuteTTS-0.2-500M
+$ cd OuteTTS-0.2-500M && git lfs install && git lfs pull
+$ popd
+```
+Convert the model to .gguf format:
+```console
+(venv) python convert_hf_to_gguf.py models/OuteTTS-0.2-500M \
+    --outfile models/outetts-0.2-0.5B-f16.gguf --outtype f16
+```
+The generated model will be `models/outetts-0.2-0.5B-f16.gguf`.
+
+We can optionally quantize this to Q8_0 using the following command:
+```console
+$ build/bin/llama-quantize models/outetts-0.2-0.5B-f16.gguf \
+    models/outetts-0.2-0.5B-q8_0.gguf q8_0
+```
+The quantized model will be `models/outetts-0.2-0.5B-q8_0.gguf`.
+
+Next we do something simlar for the audio decoder. First download or checkout
+the model for the voice decoder:
+```console
+$ pushd models
+$ git clone --branch main --single-branch --depth 1 https://huggingface.co/novateur/WavTokenizer-large-speech-75token
+$ cd WavTokenizer-large-speech-75token && git lfs install && git lfs pull
+$ popd
+```
+This model file is PyTorch checkpoint (.ckpt) and we first need to convert it to
+huggingface format:
+```console
+(venv) python examples/tts/convert_pt_to_hf.py \
+    models/WavTokenizer-large-speech-75token/wavtokenizer_large_speech_320_24k.ckpt
+...
+Model has been successfully converted and saved to models/WavTokenizer-large-speech-75token/model.safetensors
+Metadata has been saved to models/WavTokenizer-large-speech-75token/index.json
+Config has been saved to models/WavTokenizer-large-speech-75tokenconfig.json
+```
+Then we can convert the huggingface format to gguf:
+```console
+(venv) python convert_hf_to_gguf.py models/WavTokenizer-large-speech-75token \
+    --outfile models/wavtokenizer-large-75-f16.gguf --outtype f16
+...
+INFO:hf-to-gguf:Model successfully exported to models/wavtokenizer-large-75-f16.gguf
+```
+
+### Running the example
+
+With both of the models generated, the LLM model and the voice decoder model,
+we can run the example:
+```console
+$ build/bin/llama-tts -m  ./models/outetts-0.2-0.5B-q8_0.gguf \
+    -mv ./models/wavtokenizer-large-75-f16.gguf \
+    -p "Hello world"
+...
+main: audio written to file 'output.wav'
+```
+The output.wav file will contain the audio of the prompt. This can be heard
+by playing the file with a media player. On Linux the following command will
+play the audio:
+```console
+$ aplay output.wav
+```
+