piper: add page (#13144)

Co-authored-by: spageektti <git@spageektti.cc>
Co-authored-by: Sebastiaan Speck <12570668+sebastiaanspeck@users.noreply.github.com>

pages/common/piper.md

@@ -0,0 +1,25 @@
+# piper
+
+> A fast, local neural text to speech system.
+> Try out and download speech models from <https://rhasspy.github.io/piper-samples>.
+> More information: <https://github.com/rhasspy/piper>.
+
+- Output a WAV [f]ile using a text-to-speech [m]odel (assuming a config file at model_path + .json):
+
+`echo {{Thing to say}} | piper -m {{path/to/model.onnx}} -f {{outputfile.wav}}`
+
+- Output a WAV [f]ile using a [m]odel and specifying its JSON [c]onfig file:
+
+`echo {{'Thing to say'}} | piper -m {{path/to/model.onnx}} -c {{path/to/model.onnx.json}} -f {{outputfile.wav}}`
+
+- Select a particular speaker in a voice with multiple speakers by specifying the speaker's ID number:
+
+`echo {{'Warum?'}} | piper -m {{de_DE-thorsten_emotional-medium.onnx}} --speaker {{1}} -f {{angry.wav}}`
+
+- Stream the output to the mpv media player:
+
+`echo {{'Hello world'}} | piper -m {{en_GB-northern_english_male-medium.onnx}} --output-raw -f - | mpv -`
+
+- Speak twice as fast, with huge gaps between sentences:
+
+`echo {{'Speaking twice the speed. With added drama!'}} | piper -m {{foo.onnx}} --length_scale {{0.5}} --sentence_silence {{2}} -f {{drama.wav}}`