Adding Watson TTS (IBM Cloud) (#9279)

* Adding Watson TTS (IBM Cloud)

* Review fixes

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source/_components/watson_tts.markdown

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+---
+layout: page
+title: "Watson TTS"
+description: "Instructions on how to setup IBM Watson TTS with Home Assistant."
+date: 2019-04-22 12:00
+sidebar: true
+comments: false
+sharing: true
+footer: true
+logo: watson_tts.png
+ha_category:
+  - Text-to-speech
+ha_release: 0.94
+---
+
+The `watson_tts` text-to-speech platform that works with [IBM Watson Cloud](https://www.ibm.com/watson/services/text-to-speech/) to create the spoken output.
+Polly is a paid service via IBM Cloud but there is a decent [free tier](https://www.ibm.com/cloud/watson-text-to-speech/pricing) which offers 10000 free characters every month.
+
+## {% linkable_title Setup %}
+
+For supported formats and voices please go to [IBM Cloud About section](https://cloud.ibm.com/docs/services/text-to-speech?topic=text-to-speech-about#about).
+
+To get started please read the [Getting started tutorial](https://cloud.ibm.com/docs/services/text-to-speech?topic=text-to-speech-gettingStarted#gettingStarted).
+
+## {% linkable_title Configuration %}
+
+To configure Watson TTS, add the following lines to your `configuration.yaml`:
+
+```yaml
+# Example configuration.yaml entry
+tts:
+  - platform: watson_tts
+    watson_apikey: YOUR_GENERATED_APIKEY
+```
+
+You can get these tokens after you generated the credentials on the IBM Cloud console:
+
+<p class='img'>
+  <img src='{{site_root}}/images/screenshots/watson_tts_screen.png' />
+</p>
+
+{% configuration %}
+watson_url:
+  description: "The endpoint to which the service will connect."
+  required: false
+  type: string
+  default: https://stream.watsonplatform.net/text-to-speech/api
+watson_apikey:
+  description: "Your secret apikey generated on the IBM Cloud admin console."
+  required: true
+  type: string
+voice:
+  description: Voice name to be used.
+  required: false
+  type: string
+  default: en-US_AllisonVoice
+output_format:
+  description: "Override the default output format. Supported formats: `audio/flac`, `audio/mp3`, `audio/mpeg`, `audio/ogg`, `audio/ogg;codecs=opus`, `audio/ogg;codecs=vorbis`, `audio/wav`"
+  required: false
+  type: string
+  default: audio/mp3
+{% endconfiguration %}
+
+## {% linkable_title Usage %}
+
+Say to all `media_player` device entities:
+
+```yaml
+- service: tts.watson_tts_say
+  data_template:
+    message: 'Hello from Watson'
+```
+
+or
+
+```yaml
+- service: tts.watson_tts_say
+  data_template:
+    message: >
+      <speak>
+          Hello from Watson
+      </speak>
+```
+
+Say to the `media_player.living_room` device entity:
+
+```yaml
+- service: tts.watson_tts_say
+  data_template:
+    entity_id: media_player.living_room
+    message: >
+      <speak>
+          Hello from Watson
+      </speak>
+```
+
+Say with break:
+
+```yaml
+- service: tts.watson_tts_say
+  data_template:
+    message: >
+      <speak>
+          Hello from
+          <break time=".9s" />
+          Watson
+      </speak>
+```