[porcupineks] Keyword Spotter, initial contribution (#12028)

* initial contribution

Signed-off-by: Miguel Álvarez Díez <miguelwork92@gmail.com>

bundles/org.openhab.voice.porcupineks/README.md

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+# Porcupine Keyword Spotter
+
+This voice service allows you to use the PicoVoice product Porcupine as your keyword spotter in openHAB.
+
+Porcupine provides on-device wake word detection powered by deep learning.
+This add-on should work on all the platforms supported by Porcupine, if you encounter a problem you can try to run one of the Porcupine java demos on your machine.
+
+Important: No voice data listened by this service will be uploaded to the Cloud.
+The voice data is processed offline, locally on your openHAB server by Porcupine.
+Once in a while, access keys are validated to stay active and this requires an Internet connection.
+
+## How to use it
+
+After installing, you will be able to access the addon options through the openHAB configuration page under the 'Other Services' section.
+There you will need to provide your PicoVoice Api Key.
+
+After that, you can select Porcupine as your default Keyword Spotter in your 'Voice' settings.
+
+## Magic Word Configuration
+
+The magic word to spot is gathered from your 'Voice' configuration. 
+The default english keyword models are loaded in the addon (also the english language model) so you can use those without adding anything else.
+
+Note that you can use the pico voice platform to generate your own keyword models. 
+To use them, you should place the generated file under '\<openHAB userdata\>/porcupine' and configure your magic word to match the file name replacing spaces with '_' and adding the extension '.ppn'.
+As an example, the file generated for the keyword "ok openhab" will be named 'ok_openhab.ppn'.
+
+The service will only work if it's able to find the correct ppn for your magic word configuration.
+
+#### Build-in keywords
+
+Remember that they only work with the English language model. (read bellow section)
+
+* alexa
+* americano
+* blueberry
+* bumblebee
+* computer
+* grapefruits
+* grasshopper
+* hey google
+* hey siri
+* jarvis
+* ok google
+* picovoice
+* porcupine
+* terminator
+
+
+## Language support
+
+This service currently supports English, German, French and Spanish. 
+
+Only the English model binary is included with the addon and will be used if the one for your configured language is not found under '\<openHAB userdata\>/porcupine'.
+
+To get the language model files, go to the [Porcupine repo](https://github.com/Picovoice/porcupine/tree/v2.0/lib/common).
+
+Note that the keyword model you use should match the language model.